diff --git a/src/Budget.Client/package-lock.json b/src/Budget.Client/package-lock.json
index 04ac015..9f2c94e 100644
--- a/src/Budget.Client/package-lock.json
+++ b/src/Budget.Client/package-lock.json
@@ -11,6 +11,7 @@
         "@dnd-kit/core": "^6.3.1",
         "@dnd-kit/sortable": "^10.0.0",
         "@dnd-kit/utilities": "^3.2.2",
+        "@tanstack/react-query": "^5.100.8",
         "oidc-client-ts": "^3.5.0",
         "react": "^19.2.5",
         "react-dom": "^19.2.5",
@@ -896,6 +897,32 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@tanstack/query-core": {
+      "version": "5.100.8",
+      "resolved": "https://registry.npmjs.org/@tanstack/query-core/-/query-core-5.100.8.tgz",
+      "integrity": "sha512-ceYwSFOqjPwET5TA6IOYxzxlGc0ekyH/gfOtWkP0PX43rzX9bxW48Iuw8KAduKCToi4rJAQ6nRy2kAe8gszdmg==",
+      "license": "MIT",
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/tannerlinsley"
+      }
+    },
+    "node_modules/@tanstack/react-query": {
+      "version": "5.100.8",
+      "resolved": "https://registry.npmjs.org/@tanstack/react-query/-/react-query-5.100.8.tgz",
+      "integrity": "sha512-iNNEekixXU5vtAGKKZX2lx3jTooG5yNY+kv0wSgEdEYG0Mj0JM5bcuQtC35ZAP3nDopT6jciUK3xeX65U7AnfA==",
+      "license": "MIT",
+      "dependencies": {
+        "@tanstack/query-core": "5.100.8"
+      },
+      "funding": {
+        "type": "github",
+        "url": "https://github.com/sponsors/tannerlinsley"
+      },
+      "peerDependencies": {
+        "react": "^18 || ^19"
+      }
+    },
     "node_modules/@tybys/wasm-util": {
       "version": "0.10.1",
       "resolved": "https://registry.npmjs.org/@tybys/wasm-util/-/wasm-util-0.10.1.tgz",
diff --git a/src/Budget.Client/package.json b/src/Budget.Client/package.json
index 5cd4cfd..efb49fe 100644
--- a/src/Budget.Client/package.json
+++ b/src/Budget.Client/package.json
@@ -13,6 +13,7 @@
     "@dnd-kit/core": "^6.3.1",
     "@dnd-kit/sortable": "^10.0.0",
     "@dnd-kit/utilities": "^3.2.2",
+    "@tanstack/react-query": "^5.100.8",
     "oidc-client-ts": "^3.5.0",
     "react": "^19.2.5",
     "react-dom": "^19.2.5",
diff --git a/src/Budget.Client/src/App.tsx b/src/Budget.Client/src/App.tsx
index 3756eed..0d33899 100644
--- a/src/Budget.Client/src/App.tsx
+++ b/src/Budget.Client/src/App.tsx
@@ -1,10 +1,13 @@
 import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom';
 import { AuthProvider } from 'react-oidc-context';
+import { QueryClientProvider } from '@tanstack/react-query';
 import { authConfig } from './auth/authConfig';
+import { queryClient } from './api/queryClient';
 import { TokenSync } from './auth/TokenSync';
 import { AuthGuard } from './auth/AuthGuard';
 import { ErrorBoundary } from './components/ErrorBoundary';
 import { ToastProvider } from './components/Toast';
+import { QueryToastBridge } from './components/QueryToastBridge';
 import { CallbackPage } from './pages/CallbackPage';
 import { BudgetsPage } from './pages/BudgetsPage';
 import { IncomePage } from './pages/IncomePage';
@@ -21,22 +24,25 @@ const onSigninCallback = () => {
 function App() {
   return (
     <ErrorBoundary>
-      <ToastProvider>
-        <AuthProvider {...authConfig} onSigninCallback={onSigninCallback}>
-          <TokenSync />
-          <BrowserRouter>
-            <Routes>
-              <Route path="/" element={<Navigate to="/budgets" replace />} />
-              <Route path="/callback" element={<CallbackPage />} />
-              <Route path="/budgets" element={<AuthGuard><BudgetsPage /></AuthGuard>} />
-              <Route path="/budgets/:id/income" element={<AuthGuard><IncomePage /></AuthGuard>} />
-              <Route path="/budgets/:id/outgo" element={<AuthGuard><OutgoPage /></AuthGuard>} />
-              <Route path="/budgets/:id/summary" element={<AuthGuard><SummaryPage /></AuthGuard>} />
-              <Route path="/budgets/:id/settings" element={<AuthGuard><SettingsPage /></AuthGuard>} />
-            </Routes>
-          </BrowserRouter>
-        </AuthProvider>
-      </ToastProvider>
+      <QueryClientProvider client={queryClient}>
+        <ToastProvider>
+          <QueryToastBridge />
+          <AuthProvider {...authConfig} onSigninCallback={onSigninCallback}>
+            <TokenSync />
+            <BrowserRouter>
+              <Routes>
+                <Route path="/" element={<Navigate to="/budgets" replace />} />
+                <Route path="/callback" element={<CallbackPage />} />
+                <Route path="/budgets" element={<AuthGuard><BudgetsPage /></AuthGuard>} />
+                <Route path="/budgets/:id/income" element={<AuthGuard><IncomePage /></AuthGuard>} />
+                <Route path="/budgets/:id/outgo" element={<AuthGuard><OutgoPage /></AuthGuard>} />
+                <Route path="/budgets/:id/summary" element={<AuthGuard><SummaryPage /></AuthGuard>} />
+                <Route path="/budgets/:id/settings" element={<AuthGuard><SettingsPage /></AuthGuard>} />
+              </Routes>
+            </BrowserRouter>
+          </AuthProvider>
+        </ToastProvider>
+      </QueryClientProvider>
     </ErrorBoundary>
   );
 }
diff --git a/src/Budget.Client/src/api/budgets.ts b/src/Budget.Client/src/api/budgets.ts
new file mode 100644
index 0000000..099f625
--- /dev/null
+++ b/src/Budget.Client/src/api/budgets.ts
@@ -0,0 +1,47 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { api } from './client';
+import type { BudgetDto } from '../types/index';
+
+interface CreateBudgetRequest { name: string; }
+interface UpdateBudgetRequest { name: string; }
+
+export function useBudgets() {
+  return useQuery({
+    queryKey: ['budgets'],
+    queryFn: () => api.get<BudgetDto[]>('/api/budgets'),
+  });
+}
+
+export function useBudget(id: string) {
+  return useQuery({
+    queryKey: ['budgets', id],
+    queryFn: () => api.get<BudgetDto>(`/api/budgets/${id}`),
+  });
+}
+
+export function useCreateBudget() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (req: CreateBudgetRequest) => api.post<BudgetDto>('/api/budgets', req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets'] }),
+    meta: { successMessage: 'Budget created', errorMessage: 'Failed to create budget' },
+  });
+}
+
+export function useUpdateBudget(id: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (req: UpdateBudgetRequest) => api.put<BudgetDto>(`/api/budgets/${id}`, req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', id] }),
+    meta: { successMessage: 'Budget saved', errorMessage: 'Failed to save budget' },
+  });
+}
+
+export function useDeleteBudget() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => api.delete(`/api/budgets/${id}`),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets'] }),
+    meta: { errorMessage: 'Failed to delete budget' },
+  });
+}
diff --git a/src/Budget.Client/src/api/incomes.ts b/src/Budget.Client/src/api/incomes.ts
new file mode 100644
index 0000000..0442c8d
--- /dev/null
+++ b/src/Budget.Client/src/api/incomes.ts
@@ -0,0 +1,51 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { api } from './client';
+import type { IncomeDto, Frequency } from '../types/index';
+
+interface CreateIncomeRequest { name: string; frequency: Frequency; amount: number; }
+interface UpdateIncomeRequest { name: string; frequency: Frequency; amount: number; }
+interface ReorderRequest { orderedIds: string[]; }
+
+export function useIncomes(budgetId: string) {
+  return useQuery({
+    queryKey: ['budgets', budgetId, 'incomes'],
+    queryFn: () => api.get<IncomeDto[]>(`/api/budgets/${budgetId}/incomes`),
+  });
+}
+
+export function useCreateIncome(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (req: CreateIncomeRequest) => api.post<IncomeDto>(`/api/budgets/${budgetId}/incomes`, req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'incomes'] }),
+    meta: { errorMessage: 'Failed to add income' },
+  });
+}
+
+export function useUpdateIncome(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, ...req }: UpdateIncomeRequest & { id: string }) =>
+      api.put<IncomeDto>(`/api/budgets/${budgetId}/incomes/${id}`, req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'incomes'] }),
+    meta: { errorMessage: 'Failed to save income' },
+  });
+}
+
+export function useDeleteIncome(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => api.delete(`/api/budgets/${budgetId}/incomes/${id}`),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'incomes'] }),
+    meta: { errorMessage: 'Failed to delete income' },
+  });
+}
+
+export function useReorderIncomes(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (req: ReorderRequest) => api.put<void>(`/api/budgets/${budgetId}/incomes/order`, req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'incomes'] }),
+    meta: { errorMessage: 'Failed to save order' },
+  });
+}
diff --git a/src/Budget.Client/src/api/outgos.ts b/src/Budget.Client/src/api/outgos.ts
new file mode 100644
index 0000000..1219276
--- /dev/null
+++ b/src/Budget.Client/src/api/outgos.ts
@@ -0,0 +1,68 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { api } from './client';
+import type { OutgoDto, Frequency, OutgoType } from '../types/index';
+
+interface CreateOutgoRequest {
+  name: string; category: string | null; type: OutgoType;
+  frequency: Frequency; amount: number; paymentSource: string | null; notes: string | null;
+}
+interface UpdateOutgoRequest extends CreateOutgoRequest { id: string; }
+interface ReorderRequest { orderedIds: string[]; }
+
+export function useOutgos(budgetId: string) {
+  return useQuery({
+    queryKey: ['budgets', budgetId, 'outgos'],
+    queryFn: () => api.get<OutgoDto[]>(`/api/budgets/${budgetId}/outgos`),
+  });
+}
+
+export function useCategories(budgetId: string) {
+  return useQuery({
+    queryKey: ['budgets', budgetId, 'outgos', 'categories'],
+    queryFn: () => api.get<string[]>(`/api/budgets/${budgetId}/outgos/categories`),
+  });
+}
+
+export function usePaymentSources(budgetId: string) {
+  return useQuery({
+    queryKey: ['budgets', budgetId, 'outgos', 'payment-sources'],
+    queryFn: () => api.get<string[]>(`/api/budgets/${budgetId}/outgos/payment-sources`),
+  });
+}
+
+export function useCreateOutgo(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (req: CreateOutgoRequest) => api.post<OutgoDto>(`/api/budgets/${budgetId}/outgos`, req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'outgos'] }),
+    meta: { errorMessage: 'Failed to add outgo' },
+  });
+}
+
+export function useUpdateOutgo(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, ...req }: UpdateOutgoRequest) =>
+      api.put<OutgoDto>(`/api/budgets/${budgetId}/outgos/${id}`, req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'outgos'] }),
+    meta: { errorMessage: 'Failed to save outgo' },
+  });
+}
+
+export function useDeleteOutgo(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => api.delete(`/api/budgets/${budgetId}/outgos/${id}`),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'outgos'] }),
+    meta: { errorMessage: 'Failed to delete outgo' },
+  });
+}
+
+export function useReorderOutgos(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (req: ReorderRequest) => api.put<void>(`/api/budgets/${budgetId}/outgos/order`, req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'outgos'] }),
+    meta: { errorMessage: 'Failed to save order' },
+  });
+}
diff --git a/src/Budget.Client/src/api/queryClient.ts b/src/Budget.Client/src/api/queryClient.ts
new file mode 100644
index 0000000..ab98f6c
--- /dev/null
+++ b/src/Budget.Client/src/api/queryClient.ts
@@ -0,0 +1,27 @@
+import { MutationCache, QueryClient } from '@tanstack/react-query';
+
+declare module '@tanstack/react-query' {
+  interface Register {
+    mutationMeta: {
+      successMessage?: string;
+      errorMessage?: string;
+    };
+  }
+}
+
+let toastHandlers: { showError: (msg: string) => void; showInfo: (msg: string) => void } | null = null;
+
+export function setToastHandlers(handlers: typeof toastHandlers) {
+  toastHandlers = handlers;
+}
+
+export const queryClient = new QueryClient({
+  mutationCache: new MutationCache({
+    onSuccess: (_data, _vars, _ctx, mutation) => {
+      if (mutation.meta?.successMessage) toastHandlers?.showInfo(mutation.meta.successMessage);
+    },
+    onError: (_err, _vars, _ctx, mutation) => {
+      toastHandlers?.showError(mutation.meta?.errorMessage ?? 'Something went wrong');
+    },
+  }),
+});
diff --git a/src/Budget.Client/src/api/shares.ts b/src/Budget.Client/src/api/shares.ts
new file mode 100644
index 0000000..3d2a63f
--- /dev/null
+++ b/src/Budget.Client/src/api/shares.ts
@@ -0,0 +1,41 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { api } from './client';
+import type { ShareDto, SharePermission } from '../types/index';
+
+interface AddShareRequest { email: string; permission: SharePermission; }
+interface UpdateShareRequest { permission: SharePermission; }
+
+export function useShares(budgetId: string) {
+  return useQuery({
+    queryKey: ['budgets', budgetId, 'shares'],
+    queryFn: () => api.get<ShareDto[]>(`/api/budgets/${budgetId}/shares`),
+  });
+}
+
+export function useAddShare(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (req: AddShareRequest) => api.post<ShareDto>(`/api/budgets/${budgetId}/shares`, req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'shares'] }),
+    meta: { successMessage: 'Share invitation sent', errorMessage: 'Failed to add share' },
+  });
+}
+
+export function useUpdateShare(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: ({ id, ...req }: UpdateShareRequest & { id: string }) =>
+      api.put<ShareDto>(`/api/budgets/${budgetId}/shares/${id}`, req),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'shares'] }),
+    meta: { errorMessage: 'Failed to update permission' },
+  });
+}
+
+export function useRevokeShare(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (id: string) => api.delete(`/api/budgets/${budgetId}/shares/${id}`),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'shares'] }),
+    meta: { errorMessage: 'Failed to revoke share' },
+  });
+}
diff --git a/src/Budget.Client/src/api/summary.ts b/src/Budget.Client/src/api/summary.ts
new file mode 100644
index 0000000..0d81bf4
--- /dev/null
+++ b/src/Budget.Client/src/api/summary.ts
@@ -0,0 +1,23 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { api } from './client';
+import type { SummaryDto } from '../types/index';
+
+export function useSummary(budgetId: string) {
+  return useQuery({
+    queryKey: ['budgets', budgetId, 'summary'],
+    queryFn: () => api.get<SummaryDto>(`/api/budgets/${budgetId}/summary`),
+  });
+}
+
+export function useUpdateTaxRate(budgetId: string) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: (effectiveTaxRate: number) =>
+      api.put<void>(`/api/budgets/${budgetId}/summary/tax-rate`, { effectiveTaxRate }),
+    onSuccess: () => {
+      qc.invalidateQueries({ queryKey: ['budgets', budgetId, 'summary'] });
+      qc.invalidateQueries({ queryKey: ['budgets', budgetId] });
+    },
+    meta: { successMessage: 'Tax rate saved', errorMessage: 'Failed to save tax rate' },
+  });
+}
diff --git a/src/Budget.Client/src/components/QueryToastBridge.tsx b/src/Budget.Client/src/components/QueryToastBridge.tsx
new file mode 100644
index 0000000..9db4652
--- /dev/null
+++ b/src/Budget.Client/src/components/QueryToastBridge.tsx
@@ -0,0 +1,11 @@
+import { useEffect } from 'react';
+import { useToast } from './Toast';
+import { setToastHandlers } from '../api/queryClient';
+
+export function QueryToastBridge() {
+  const { showError, showInfo } = useToast();
+  useEffect(() => {
+    setToastHandlers({ showError, showInfo });
+  }, [showError, showInfo]);
+  return null;
+}
diff --git a/src/Budget.Client/src/pages/BudgetsPage.tsx b/src/Budget.Client/src/pages/BudgetsPage.tsx
index 2e89cf9..9522f2c 100644
--- a/src/Budget.Client/src/pages/BudgetsPage.tsx
+++ b/src/Budget.Client/src/pages/BudgetsPage.tsx
@@ -1,21 +1,16 @@
-import { useEffect, useState } from 'react';
+import { useState } from 'react';
 import { useNavigate } from 'react-router-dom';
-import type { BudgetDto } from '../types';
-import { api } from '../api/client';
+import { useBudgets, useCreateBudget } from '../api/budgets';
 
 export function BudgetsPage() {
-  const [budgets, setBudgets] = useState<BudgetDto[]>([]);
   const [newName, setNewName] = useState('');
   const navigate = useNavigate();
-
-  useEffect(() => {
-    api.get<BudgetDto[]>('/api/budgets').then(setBudgets);
-  }, []);
+  const { data: budgets = [] } = useBudgets();
+  const createBudget = useCreateBudget();
 
   const handleCreate = async () => {
     if (!newName.trim()) return;
-    const created = await api.post<BudgetDto>('/api/budgets', { name: newName.trim() });
-    setBudgets(prev => [...prev, created]);
+    const created = await createBudget.mutateAsync({ name: newName.trim() });
     setNewName('');
     navigate(`/budgets/${created.id}/income`);
   };
diff --git a/src/Budget.Client/src/pages/IncomePage.tsx b/src/Budget.Client/src/pages/IncomePage.tsx
index 4db679b..499b961 100644
--- a/src/Budget.Client/src/pages/IncomePage.tsx
+++ b/src/Budget.Client/src/pages/IncomePage.tsx
@@ -1,6 +1,5 @@
-import { useEffect, useState } from 'react';
+import { useState, useEffect } from 'react';
 import { useParams } from 'react-router-dom';
-import { useToast } from '../components/Toast';
 import { LoadingSkeleton } from '../components/LoadingSkeleton';
 import {
   DndContext,
@@ -17,11 +16,11 @@ import {
   arrayMove,
 } from '@dnd-kit/sortable';
 import { CSS } from '@dnd-kit/utilities';
-import type { IncomeDto, Frequency } from '../types';
-import { api } from '../api/client';
+import type { IncomeDto, Frequency } from '../types/index';
 import { FrequencySelect } from '../components/FrequencySelect';
 import { MoneyDisplay } from '../components/MoneyDisplay';
 import { BudgetNav } from '../components/BudgetNav';
+import { useIncomes, useCreateIncome, useUpdateIncome, useDeleteIncome, useReorderIncomes } from '../api/incomes';
 
 interface EditState {
   name: string;
@@ -88,61 +87,41 @@ function SortableRow({
 
 export function IncomePage() {
   const { id: budgetId } = useParams<{ id: string }>();
-  const [incomes, setIncomes] = useState<IncomeDto[]>([]);
-  const [loading, setLoading] = useState(true);
-  const { showError } = useToast();
   const sensors = useSensors(useSensor(PointerSensor));
 
-  useEffect(() => {
-    if (!budgetId) return;
-    setLoading(true);
-    api.get<IncomeDto[]>(`/api/budgets/${budgetId}/incomes`)
-      .then(setIncomes)
-      .catch(e => showError(String(e)))
-      .finally(() => setLoading(false));
-  }, [budgetId]);
+  const { data: incomes = [], isLoading } = useIncomes(budgetId!);
+  const [displayItems, setDisplayItems] = useState<IncomeDto[]>([]);
+  useEffect(() => { setDisplayItems(incomes); }, [incomes]);
 
-  const handleSave = async (id: string, edit: EditState) => {
-    try {
-      const updated = await api.put<IncomeDto>(`/api/budgets/${budgetId}/incomes/${id}`, {
-        name: edit.name,
-        frequency: edit.frequency,
-        amount: parseFloat(edit.amount),
-      });
-      setIncomes(prev => prev.map(i => i.id === id ? updated : i));
-    } catch (e) { showError(String(e)); }
+  const updateIncome = useUpdateIncome(budgetId!);
+  const deleteIncome = useDeleteIncome(budgetId!);
+  const createIncome = useCreateIncome(budgetId!);
+  const reorderIncomes = useReorderIncomes(budgetId!);
+
+  const handleSave = (id: string, edit: EditState) => {
+    updateIncome.mutate({ id, name: edit.name, frequency: edit.frequency, amount: parseFloat(edit.amount) });
   };
 
-  const handleDelete = async (id: string) => {
+  const handleDelete = (id: string) => {
     if (!confirm('Delete this income row?')) return;
-    try {
-      await api.delete(`/api/budgets/${budgetId}/incomes/${id}`);
-      setIncomes(prev => prev.filter(i => i.id !== id));
-    } catch (e) { showError(String(e)); }
+    deleteIncome.mutate(id);
   };
 
-  const handleAdd = async () => {
-    const created = await api.post<IncomeDto>(`/api/budgets/${budgetId}/incomes`, {
-      name: 'New Income',
-      frequency: 'Monthly',
-      amount: 0,
-    });
-    setIncomes(prev => [...prev, created]);
+  const handleAdd = () => {
+    createIncome.mutate({ name: 'New Income', frequency: 'Monthly', amount: 0 });
   };
 
-  const handleDragEnd = async (event: DragEndEvent) => {
+  const handleDragEnd = (event: DragEndEvent) => {
     const { active, over } = event;
     if (!over || active.id === over.id) return;
-    const oldIdx = incomes.findIndex(i => i.id === active.id);
-    const newIdx = incomes.findIndex(i => i.id === over.id);
-    const reordered = arrayMove(incomes, oldIdx, newIdx);
-    setIncomes(reordered);
-    await api.put(`/api/budgets/${budgetId}/incomes/order`, {
-      orderedIds: reordered.map(i => i.id),
-    });
+    const oldIdx = displayItems.findIndex(i => i.id === active.id);
+    const newIdx = displayItems.findIndex(i => i.id === over.id);
+    const reordered = arrayMove(displayItems, oldIdx, newIdx);
+    setDisplayItems(reordered);
+    reorderIncomes.mutate({ orderedIds: reordered.map(i => i.id) });
   };
 
-  if (loading) return <><BudgetNav /><LoadingSkeleton rows={5} cols={6} /></>;
+  if (isLoading) return <><BudgetNav /><LoadingSkeleton rows={5} cols={6} /></>;
 
   return (
     <div>
@@ -161,9 +140,9 @@ export function IncomePage() {
           </tr>
         </thead>
         <DndContext sensors={sensors} collisionDetection={closestCenter} onDragEnd={handleDragEnd}>
-          <SortableContext items={incomes.map(i => i.id)} strategy={verticalListSortingStrategy}>
+          <SortableContext items={displayItems.map(i => i.id)} strategy={verticalListSortingStrategy}>
             <tbody>
-              {incomes.map(income => (
+              {displayItems.map(income => (
                 <SortableRow
                   key={income.id}
                   income={income}
diff --git a/src/Budget.Client/src/pages/OutgoPage.tsx b/src/Budget.Client/src/pages/OutgoPage.tsx
index 7dc266d..7a187f9 100644
--- a/src/Budget.Client/src/pages/OutgoPage.tsx
+++ b/src/Budget.Client/src/pages/OutgoPage.tsx
@@ -1,6 +1,5 @@
-import { useEffect, useState } from 'react';
+import { useState, useEffect } from 'react';
 import { useParams } from 'react-router-dom';
-import { useToast } from '../components/Toast';
 import { LoadingSkeleton } from '../components/LoadingSkeleton';
 import {
   DndContext,
@@ -17,12 +16,15 @@ import {
   arrayMove,
 } from '@dnd-kit/sortable';
 import { CSS } from '@dnd-kit/utilities';
-import type { OutgoDto, Frequency, OutgoType } from '../types';
-import { api } from '../api/client';
+import type { OutgoDto, Frequency, OutgoType } from '../types/index';
 import { FrequencySelect } from '../components/FrequencySelect';
 import { MoneyDisplay } from '../components/MoneyDisplay';
 import { AutocompleteInput } from '../components/AutocompleteInput';
 import { BudgetNav } from '../components/BudgetNav';
+import {
+  useOutgos, useCategories, usePaymentSources,
+  useCreateOutgo, useUpdateOutgo, useDeleteOutgo, useReorderOutgos,
+} from '../api/outgos';
 
 const OUTGO_TYPES: OutgoType[] = ['Need', 'Want', 'Save'];
 
@@ -129,83 +131,60 @@ function SortableRow({
 
 export function OutgoPage() {
   const { id: budgetId } = useParams<{ id: string }>();
-  const [outgos, setOutgos] = useState<OutgoDto[]>([]);
-  const [categories, setCategories] = useState<string[]>([]);
-  const [paymentSources, setPaymentSources] = useState<string[]>([]);
-  const [loading, setLoading] = useState(true);
-  const { showError } = useToast();
   const sensors = useSensors(useSensor(PointerSensor));
 
-  useEffect(() => {
-    if (!budgetId) return;
-    setLoading(true);
-    Promise.all([
-      api.get<OutgoDto[]>(`/api/budgets/${budgetId}/outgos`),
-      api.get<string[]>(`/api/budgets/${budgetId}/outgos/categories`),
-      api.get<string[]>(`/api/budgets/${budgetId}/outgos/payment-sources`),
-    ]).then(([o, c, p]) => { setOutgos(o); setCategories(c); setPaymentSources(p); })
-      .catch(e => showError(String(e)))
-      .finally(() => setLoading(false));
-  }, [budgetId]);
+  const { data: outgos = [], isLoading } = useOutgos(budgetId!);
+  const { data: categories = [] } = useCategories(budgetId!);
+  const { data: paymentSources = [] } = usePaymentSources(budgetId!);
+  const [displayItems, setDisplayItems] = useState<OutgoDto[]>([]);
+  useEffect(() => { setDisplayItems(outgos); }, [outgos]);
 
-  const refreshSuggestions = () => {
-    if (!budgetId) return;
-    api.get<string[]>(`/api/budgets/${budgetId}/outgos/categories`).then(setCategories);
-    api.get<string[]>(`/api/budgets/${budgetId}/outgos/payment-sources`).then(setPaymentSources);
-  };
+  const updateOutgo = useUpdateOutgo(budgetId!);
+  const deleteOutgo = useDeleteOutgo(budgetId!);
+  const createOutgo = useCreateOutgo(budgetId!);
+  const reorderOutgos = useReorderOutgos(budgetId!);
 
-  const handleSave = async (id: string, edit: EditState) => {
-    try {
-      const updated = await api.put<OutgoDto>(`/api/budgets/${budgetId}/outgos/${id}`, {
-        name: edit.name,
-        category: edit.category || null,
-        type: edit.type,
-        frequency: edit.frequency,
-        amount: parseFloat(edit.amount),
-        paymentSource: edit.paymentSource || null,
-        notes: edit.notes || null,
-      });
-      setOutgos(prev => prev.map(o => o.id === id ? updated : o));
-      refreshSuggestions();
-    } catch (e) { showError(String(e)); }
-  };
-
-  const handleDelete = async (id: string) => {
-    if (!confirm('Delete this outgo row?')) return;
-    try {
-      await api.delete(`/api/budgets/${budgetId}/outgos/${id}`);
-      setOutgos(prev => prev.filter(o => o.id !== id));
-    } catch (e) { showError(String(e)); }
-  };
-
-  const handleAdd = async () => {
-    try {
-      const created = await api.post<OutgoDto>(`/api/budgets/${budgetId}/outgos`, {
-        name: 'New Outgo',
-        category: null,
-        type: 'Need',
-        frequency: 'Monthly',
-        amount: 0,
-        paymentSource: null,
-        notes: null,
-      });
-      setOutgos(prev => [...prev, created]);
-    } catch (e) { showError(String(e)); }
-  };
-
-  const handleDragEnd = async (event: DragEndEvent) => {
-    const { active, over } = event;
-    if (!over || active.id === over.id) return;
-    const oldIdx = outgos.findIndex(o => o.id === active.id);
-    const newIdx = outgos.findIndex(o => o.id === over.id);
-    const reordered = arrayMove(outgos, oldIdx, newIdx);
-    setOutgos(reordered);
-    await api.put(`/api/budgets/${budgetId}/outgos/order`, {
-      orderedIds: reordered.map(o => o.id),
+  const handleSave = (id: string, edit: EditState) => {
+    updateOutgo.mutate({
+      id,
+      name: edit.name,
+      category: edit.category || null,
+      type: edit.type,
+      frequency: edit.frequency,
+      amount: parseFloat(edit.amount),
+      paymentSource: edit.paymentSource || null,
+      notes: edit.notes || null,
     });
   };
 
-  if (loading) return <><BudgetNav /><LoadingSkeleton rows={5} cols={9} /></>;
+  const handleDelete = (id: string) => {
+    if (!confirm('Delete this outgo row?')) return;
+    deleteOutgo.mutate(id);
+  };
+
+  const handleAdd = () => {
+    createOutgo.mutate({
+      name: 'New Outgo',
+      category: null,
+      type: 'Need',
+      frequency: 'Monthly',
+      amount: 0,
+      paymentSource: null,
+      notes: null,
+    });
+  };
+
+  const handleDragEnd = (event: DragEndEvent) => {
+    const { active, over } = event;
+    if (!over || active.id === over.id) return;
+    const oldIdx = displayItems.findIndex(o => o.id === active.id);
+    const newIdx = displayItems.findIndex(o => o.id === over.id);
+    const reordered = arrayMove(displayItems, oldIdx, newIdx);
+    setDisplayItems(reordered);
+    reorderOutgos.mutate({ orderedIds: reordered.map(o => o.id) });
+  };
+
+  if (isLoading) return <><BudgetNav /><LoadingSkeleton rows={5} cols={9} /></>;
 
   return (
     <div>
@@ -230,9 +209,9 @@ export function OutgoPage() {
             </tr>
           </thead>
           <DndContext sensors={sensors} collisionDetection={closestCenter} onDragEnd={handleDragEnd}>
-            <SortableContext items={outgos.map(o => o.id)} strategy={verticalListSortingStrategy}>
+            <SortableContext items={displayItems.map(o => o.id)} strategy={verticalListSortingStrategy}>
               <tbody>
-                {outgos.map(outgo => (
+                {displayItems.map(outgo => (
                   <SortableRow
                     key={outgo.id}
                     outgo={outgo}
diff --git a/src/Budget.Client/src/pages/SettingsPage.tsx b/src/Budget.Client/src/pages/SettingsPage.tsx
index 41da328..d0902cd 100644
--- a/src/Budget.Client/src/pages/SettingsPage.tsx
+++ b/src/Budget.Client/src/pages/SettingsPage.tsx
@@ -1,69 +1,49 @@
-import { useEffect, useState } from 'react';
+import { useState, useEffect } from 'react';
 import { useParams } from 'react-router-dom';
-import type { BudgetDto, ShareDto, SharePermission } from '../types';
-import { api } from '../api/client';
+import type { SharePermission } from '../types/index';
 import { BudgetNav } from '../components/BudgetNav';
+import { useBudget, useUpdateBudget } from '../api/budgets';
+import { useUpdateTaxRate } from '../api/summary';
+import { useShares, useAddShare, useUpdateShare, useRevokeShare } from '../api/shares';
 
 export function SettingsPage() {
   const { id: budgetId } = useParams<{ id: string }>();
-  const [budget, setBudget] = useState<BudgetDto | null>(null);
-  const [shares, setShares] = useState<ShareDto[]>([]);
+  const { data: budget } = useBudget(budgetId!);
+  const { data: shares = [] } = useShares(budgetId!);
+
   const [nameInput, setNameInput] = useState('');
   const [taxInput, setTaxInput] = useState('');
   const [shareEmail, setShareEmail] = useState('');
   const [sharePermission, setSharePermission] = useState<SharePermission>('View');
-  const [saving, setSaving] = useState(false);
 
   useEffect(() => {
-    if (!budgetId) return;
-    api.get<BudgetDto>(`/api/budgets/${budgetId}`).then(b => {
-      setBudget(b);
-      setNameInput(b.name);
-      setTaxInput(String(Math.round(b.effectiveTaxRate * 100)));
-    });
-    api.get<ShareDto[]>(`/api/budgets/${budgetId}/shares`).then(setShares);
-  }, [budgetId]);
+    if (budget) {
+      setNameInput(budget.name);
+      setTaxInput(String(Math.round(budget.effectiveTaxRate * 100)));
+    }
+  }, [budget]);
 
-  const saveName = async () => {
-    if (!budgetId || !nameInput.trim()) return;
-    setSaving(true);
-    const updated = await api.put<BudgetDto>(`/api/budgets/${budgetId}`, { name: nameInput.trim() });
-    setBudget(updated);
-    setSaving(false);
+  const updateBudget = useUpdateBudget(budgetId!);
+  const updateTaxRate = useUpdateTaxRate(budgetId!);
+  const addShare = useAddShare(budgetId!);
+  const updateShare = useUpdateShare(budgetId!);
+  const revokeShare = useRevokeShare(budgetId!);
+
+  const saveName = () => {
+    if (!nameInput.trim()) return;
+    updateBudget.mutate({ name: nameInput.trim() });
   };
 
-  const saveTaxRate = async () => {
-    if (!budgetId) return;
-    setSaving(true);
-    const rate = parseFloat(taxInput) / 100;
-    await api.put(`/api/budgets/${budgetId}/summary/tax-rate`, { effectiveTaxRate: rate });
-    const updated = await api.get<BudgetDto>(`/api/budgets/${budgetId}`);
-    setBudget(updated);
-    setSaving(false);
+  const saveTaxRate = () => {
+    updateTaxRate.mutate(parseFloat(taxInput) / 100);
   };
 
-  const addShare = async () => {
-    if (!budgetId || !shareEmail.trim()) return;
-    const share = await api.post<ShareDto>(`/api/budgets/${budgetId}/shares`, {
-      email: shareEmail.trim(),
-      permission: sharePermission,
-    });
-    setShares(prev => [...prev, share]);
+  const handleAddShare = () => {
+    if (!shareEmail.trim()) return;
+    addShare.mutate({ email: shareEmail.trim(), permission: sharePermission });
     setShareEmail('');
   };
 
-  const updatePermission = async (shareId: string, permission: SharePermission) => {
-    if (!budgetId) return;
-    const updated = await api.put<ShareDto>(`/api/budgets/${budgetId}/shares/${shareId}`, { permission });
-    setShares(prev => prev.map(s => s.id === shareId ? updated : s));
-  };
-
-  const revokeShare = async (shareId: string) => {
-    if (!budgetId) return;
-    await api.delete(`/api/budgets/${budgetId}/shares/${shareId}`);
-    setShares(prev => prev.filter(s => s.id !== shareId));
-  };
-
   if (!budget) return <div>Loading...</div>;
 
   return (
@@ -74,7 +54,7 @@ export function SettingsPage() {
       <section style={{ marginBottom: '2rem' }}>
         <h2>Rename Budget</h2>
         <input value={nameInput} onChange={e => setNameInput(e.target.value)} />
-        <button onClick={saveName} disabled={saving} style={{ marginLeft: '8px' }}>Save</button>
+        <button onClick={saveName} disabled={updateBudget.isPending} style={{ marginLeft: '8px' }}>Save</button>
       </section>
 
       <section style={{ marginBottom: '2rem' }}>
@@ -89,7 +69,7 @@ export function SettingsPage() {
             onChange={e => setTaxInput(e.target.value)}
             style={{ width: '60px' }}
           />
-          <button onClick={saveTaxRate} disabled={saving} style={{ marginLeft: '8px' }}>Save</button>
+          <button onClick={saveTaxRate} disabled={updateTaxRate.isPending} style={{ marginLeft: '8px' }}>Save</button>
         </label>
       </section>
 
@@ -111,14 +91,14 @@ export function SettingsPage() {
                 <td>
                   <select
                     value={s.permission}
-                    onChange={e => updatePermission(s.id, e.target.value as SharePermission)}
+                    onChange={e => updateShare.mutate({ id: s.id, permission: e.target.value as SharePermission })}
                   >
                     <option value="View">View</option>
                     <option value="Edit">Edit</option>
                   </select>
                 </td>
                 <td>{s.isPending ? <em>Pending</em> : 'Active'}</td>
-                <td><button onClick={() => revokeShare(s.id)}>Revoke</button></td>
+                <td><button onClick={() => revokeShare.mutate(s.id)}>Revoke</button></td>
               </tr>
             ))}
           </tbody>
@@ -134,7 +114,7 @@ export function SettingsPage() {
             <option value="View">View</option>
             <option value="Edit">Edit</option>
           </select>
-          <button onClick={addShare}>Add Share</button>
+          <button onClick={handleAddShare}>Add Share</button>
         </div>
       </section>
     </div>
diff --git a/src/Budget.Client/src/pages/SummaryPage.tsx b/src/Budget.Client/src/pages/SummaryPage.tsx
index 8d78abd..fb8447a 100644
--- a/src/Budget.Client/src/pages/SummaryPage.tsx
+++ b/src/Budget.Client/src/pages/SummaryPage.tsx
@@ -1,34 +1,25 @@
-import { useEffect, useState } from 'react';
+import { useState, useEffect } from 'react';
 import { useParams } from 'react-router-dom';
-import type { SummaryDto } from '../types';
-import { api } from '../api/client';
 import { MoneyDisplay } from '../components/MoneyDisplay';
 import { BudgetNav } from '../components/BudgetNav';
+import { useSummary, useUpdateTaxRate } from '../api/summary';
 
 const fmt = new Intl.NumberFormat('en-US', { style: 'currency', currency: 'USD' });
 
 export function SummaryPage() {
   const { id: budgetId } = useParams<{ id: string }>();
-  const [summary, setSummary] = useState<SummaryDto | null>(null);
+  const { data: summary } = useSummary(budgetId!);
   const [taxRateInput, setTaxRateInput] = useState('');
-  const [savingTax, setSavingTax] = useState(false);
+  const updateTaxRate = useUpdateTaxRate(budgetId!);
 
   useEffect(() => {
-    if (!budgetId) return;
-    api.get<SummaryDto>(`/api/budgets/${budgetId}/summary`).then(s => {
-      setSummary(s);
-      setTaxRateInput(String(Math.round(s.preTaxIncome.effectiveTaxRate * 100)));
-    });
-  }, [budgetId]);
+    if (summary) {
+      setTaxRateInput(String(Math.round(summary.preTaxIncome.effectiveTaxRate * 100)));
+    }
+  }, [summary]);
 
-  const saveTaxRate = async () => {
-    if (!budgetId || !summary) return;
-    setSavingTax(true);
-    const rate = parseFloat(taxRateInput) / 100;
-    await api.put(`/api/budgets/${budgetId}/summary/tax-rate`, { effectiveTaxRate: rate });
-    const updated = await api.get<SummaryDto>(`/api/budgets/${budgetId}/summary`);
-    setSummary(updated);
-    setSavingTax(false);
+  const saveTaxRate = () => {
+    updateTaxRate.mutate(parseFloat(taxRateInput) / 100);
   };
 
   if (!summary) return <div>Loading...</div>;
@@ -96,8 +87,8 @@ export function SummaryPage() {
               onChange={e => setTaxRateInput(e.target.value)}
               style={{ width: '60px' }}
             />
-            <button onClick={saveTaxRate} disabled={savingTax} style={{ marginLeft: '8px' }}>
-              {savingTax ? 'Saving…' : 'Save'}
+            <button onClick={saveTaxRate} disabled={updateTaxRate.isPending} style={{ marginLeft: '8px' }}>
+              {updateTaxRate.isPending ? 'Saving…' : 'Save'}
             </button>
           </label>
         </div>