diff --git a/client/pages/SummaryPage.jsx b/client/pages/SummaryPage.tsx
similarity index 85%
rename from client/pages/SummaryPage.jsx
rename to client/pages/SummaryPage.tsx
index dc64025..c438291 100644
--- a/client/pages/SummaryPage.jsx
+++ b/client/pages/SummaryPage.tsx
@@ -1,4 +1,4 @@
-import React, { useCallback, useEffect, useMemo, useState } from 'react';
+import { useCallback, useEffect, useMemo, useState, type DragEvent, type DragEventHandler } from 'react';
 import { useQueryClient } from '@tanstack/react-query';
 import { useSummary } from '@/hooks/useQueries';
 import { toast } from 'sonner';
@@ -22,22 +22,87 @@ import { Button } from '@/components/ui/button';
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card';
 import { Input } from '@/components/ui/input';
 import { Tooltip, TooltipContent, TooltipProvider, TooltipTrigger } from '@/components/ui/tooltip';
-import { cn, fmt } from '@/lib/utils';
+import { cn, errMessage } from '@/lib/utils';
+import { formatUSD, asDollars } from '@/lib/money';
 import { moveInArray, reorderPayload } from '@/lib/reorder';
 
+function fmt(v: number | null | undefined): string {
+  return formatUSD(asDollars(Number(v) || 0));
+}
+
+interface SummaryExpense {
+  bill_id: number;
+  name: string;
+  category_name?: string | null;
+  due_day?: number | null;
+  autopay_enabled?: number;
+  is_subscription?: number;
+  has_merchant_rule?: unknown;
+  has_linked_transactions?: unknown;
+  is_paid?: boolean;
+  is_skipped?: boolean;
+  actual_amount?: number | null;
+  display_amount?: number;
+}
+
+interface SummaryChartRow {
+  type: string;
+  amount: number;
+}
+
+interface StartingAmounts {
+  first_amount?: number;
+  fifteenth_amount?: number;
+  other_amount?: number;
+  combined_amount?: number;
+  paid_total?: number;
+  combined_remaining?: number;
+}
+
+interface SummarySummary {
+  expense_total?: number;
+  result?: number;
+  paid_expense_count?: number;
+  expense_count?: number;
+  [key: string]: unknown;
+}
+
+interface SummaryResponse {
+  year: number;
+  month: number;
+  summary?: SummarySummary;
+  expenses?: SummaryExpense[];
+  starting_amounts?: StartingAmounts;
+  income?: { amount?: number; label?: string };
+  chart?: SummaryChartRow[];
+  generated_at?: string;
+  previous_month?: { combined_remaining?: number };
+  [key: string]: unknown;
+}
+
+interface ExpenseMoveControls {
+  enabled: boolean;
+  moving: boolean;
+  canMoveUp: boolean;
+  canMoveDown: boolean;
+  onMoveUp: () => void;
+  onMoveDown: () => void;
+}
+
+interface ExpenseDragProps {
+  draggable: boolean;
+  isDragging?: boolean;
+  isDropTarget?: boolean;
+  onDragStart?: DragEventHandler<HTMLDivElement>;
+  onDragEnter?: DragEventHandler<HTMLDivElement>;
+  onDragOver?: DragEventHandler<HTMLDivElement>;
+  onDragEnd?: DragEventHandler<HTMLDivElement>;
+  onDrop?: DragEventHandler<HTMLDivElement>;
+}
+
 const MONTHS = [
-  'January',
-  'February',
-  'March',
-  'April',
-  'May',
-  'June',
-  'July',
-  'August',
-  'September',
-  'October',
-  'November',
-  'December',
+  'January', 'February', 'March', 'April', 'May', 'June',
+  'July', 'August', 'September', 'October', 'November', 'December',
 ];
 
 function selectedFromToday() {
@@ -45,20 +110,20 @@ function selectedFromToday() {
   return { year: now.getFullYear(), month: now.getMonth() + 1 };
 }
 
-function shiftMonth(year, month, delta) {
+function shiftMonth(year: number, month: number, delta: number) {
   const next = new Date(year, month - 1 + delta, 1);
   return { year: next.getFullYear(), month: next.getMonth() + 1 };
 }
 
-function monthLabel(year, month) {
+function monthLabel(year: number, month: number): string {
   return `${MONTHS[month - 1]} ${year}`;
 }
 
-function moneyClass(value) {
+function moneyClass(value: number): string {
   return value >= 0 ? 'text-emerald-600 dark:text-emerald-400' : 'text-destructive';
 }
 
-function StatusMark({ expense }) {
+function StatusMark({ expense }: { expense: SummaryExpense }) {
   if (expense.is_skipped) {
     return (
       <span className="inline-flex min-w-16 items-center justify-center rounded-full bg-muted px-2 py-1 text-xs font-medium text-muted-foreground">
@@ -84,7 +149,7 @@ function StatusMark({ expense }) {
   );
 }
 
-function SummaryChart({ rows = [], onStartingClick }) {
+function SummaryChart({ rows = [], onStartingClick }: { rows?: SummaryChartRow[]; onStartingClick?: () => void }) {
   const max = Math.max(1, ...rows.map(row => Math.abs(Number(row.amount) || 0)));
   const chartRows = rows.map((row, index) => ({
     ...row,
@@ -138,7 +203,11 @@ function SummaryChart({ rows = [], onStartingClick }) {
   );
 }
 
-function ExpenseRow({ expense, moveControls, dragProps }) {
+function ExpenseRow({ expense, moveControls, dragProps }: {
+  expense: SummaryExpense;
+  moveControls?: ExpenseMoveControls;
+  dragProps?: ExpenseDragProps;
+}) {
   return (
     <div
       draggable={dragProps?.draggable}
@@ -189,7 +258,7 @@ function ExpenseRow({ expense, moveControls, dragProps }) {
         <div className="flex flex-wrap items-center gap-1.5">
           <span className="truncate text-sm font-semibold text-foreground">{expense.name}</span>
           <TooltipProvider delayDuration={300}>
-            {expense.autopay_enabled && (
+            {expense.autopay_enabled ? (
               <Tooltip>
                 <TooltipTrigger asChild>
                   <span className="inline-flex shrink-0 rounded border border-sky-500/25 bg-sky-500/10 px-1.5 py-0.5 text-[10px] font-bold leading-none text-sky-600 dark:text-sky-300 cursor-default">
@@ -198,8 +267,8 @@ function ExpenseRow({ expense, moveControls, dragProps }) {
                 </TooltipTrigger>
                 <TooltipContent>Autopay enabled</TooltipContent>
               </Tooltip>
-            )}
-            {expense.is_subscription && (
+            ) : null}
+            {expense.is_subscription ? (
               <Tooltip>
                 <TooltipTrigger asChild>
                   <span className="inline-flex shrink-0 rounded border border-indigo-500/25 bg-indigo-500/10 px-1.5 py-0.5 text-[10px] font-bold leading-none text-indigo-600 dark:text-indigo-300 cursor-default">
@@ -208,8 +277,8 @@ function ExpenseRow({ expense, moveControls, dragProps }) {
                 </TooltipTrigger>
                 <TooltipContent>Subscription</TooltipContent>
               </Tooltip>
-            )}
-            {(expense.has_merchant_rule || expense.has_linked_transactions) && (
+            ) : null}
+            {(expense.has_merchant_rule || expense.has_linked_transactions) ? (
               <Tooltip>
                 <TooltipTrigger asChild>
                   <span className="inline-flex shrink-0 rounded border border-emerald-500/25 bg-emerald-500/10 px-1.5 py-0.5 text-[10px] font-bold leading-none text-emerald-600 dark:text-emerald-400 cursor-default">
@@ -218,7 +287,7 @@ function ExpenseRow({ expense, moveControls, dragProps }) {
                 </TooltipTrigger>
                 <TooltipContent>Linked to bank transactions</TooltipContent>
               </Tooltip>
-            )}
+            ) : null}
           </TooltipProvider>
         </div>
         <div className="mt-1 flex flex-wrap items-center gap-2 text-xs text-muted-foreground">
@@ -238,9 +307,13 @@ function ExpenseRow({ expense, moveControls, dragProps }) {
 export default function SummaryPage() {
   const [selected, setSelected] = useState(selectedFromToday);
   const queryClient = useQueryClient();
-  const { data = null, isPending: loading, error: queryError } = useSummary(selected.year, selected.month);
-  const setData = useCallback((u) => queryClient.setQueryData(['summary', selected.year, selected.month],
-    prev => (typeof u === 'function' ? u(prev) : u)), [queryClient, selected.year, selected.month]);
+  const { data: dataRaw, isPending: loading, error: queryError } = useSummary(selected.year, selected.month);
+  const data = (dataRaw ?? null) as SummaryResponse | null;
+  const setData = useCallback(
+    (updater: (prev: SummaryResponse | null | undefined) => SummaryResponse | null | undefined) =>
+      queryClient.setQueryData<SummaryResponse | null>(['summary', selected.year, selected.month], updater),
+    [queryClient, selected.year, selected.month],
+  );
   const [saving, setSaving] = useState(false);
   const error = queryError ? (queryError.message || 'Summary could not be loaded.') : '';
   const [startingFirst, setStartingFirst] = useState('0');
@@ -250,9 +323,9 @@ export default function SummaryPage() {
   const [incomeAmount, setIncomeAmount] = useState('0');
   const [incomeLabel,  setIncomeLabel]  = useState('Salary');
   const [editingIncome, setEditingIncome] = useState(false);
-  const [draggingId, setDraggingId] = useState(null);
-  const [dropTargetId, setDropTargetId] = useState(null);
-  const [movingBillId, setMovingBillId] = useState(null);
+  const [draggingId, setDraggingId] = useState<number | null>(null);
+  const [dropTargetId, setDropTargetId] = useState<number | null>(null);
+  const [movingBillId, setMovingBillId] = useState<number | null>(null);
 
   const loadSummary = useCallback(
     () => queryClient.invalidateQueries({ queryKey: ['summary', selected.year, selected.month] }),
@@ -260,8 +333,7 @@ export default function SummaryPage() {
   );
 
   // Seed the editable form fields (starting amounts, income) from the loaded
-  // summary and reset transient edit/drag state whenever the data changes —
-  // this is what loadSummary used to do inline.
+  // summary and reset transient edit/drag state whenever the data changes.
   useEffect(() => {
     if (!data) return;
     setStartingFirst(String(data.starting_amounts?.first_amount ?? 0));
@@ -307,7 +379,7 @@ export default function SummaryPage() {
       toast.success('Starting amounts saved.');
       await loadSummary();
     } catch (err) {
-      toast.error(err.message || 'Starting amounts could not be saved.');
+      toast.error(errMessage(err, 'Starting amounts could not be saved.'));
     } finally {
       setSaving(false);
     }
@@ -327,13 +399,13 @@ export default function SummaryPage() {
       setEditingIncome(false);
       await loadSummary();
     } catch (err) {
-      toast.error(err.message || 'Income could not be saved.');
+      toast.error(errMessage(err, 'Income could not be saved.'));
     } finally {
       setSaving(false);
     }
   }
 
-  function moveMonth(delta) {
+  function moveMonth(delta: number) {
     setSelected(current => shiftMonth(current.year, current.month, delta));
   }
 
@@ -341,7 +413,7 @@ export default function SummaryPage() {
     setSelected(selectedFromToday());
   }
 
-  async function persistExpenseOrder(nextExpenses, movedId) {
+  async function persistExpenseOrder(nextExpenses: SummaryExpense[], movedId: number | null) {
     setData(prev => prev ? { ...prev, expenses: nextExpenses } : prev);
     setMovingBillId(movedId);
     try {
@@ -349,20 +421,20 @@ export default function SummaryPage() {
       toast.success('Summary order saved');
       await loadSummary();
     } catch (err) {
-      toast.error(err.message || 'Failed to save summary order.');
+      toast.error(errMessage(err, 'Failed to save summary order.'));
       await loadSummary();
     } finally {
       setMovingBillId(null);
     }
   }
 
-  function reorderExpenses(fromIndex, toIndex) {
+  function reorderExpenses(fromIndex: number, toIndex: number) {
     if (!reorderEnabled || fromIndex === toIndex) return;
     const nextExpenses = moveInArray(expenses, fromIndex, toIndex);
     persistExpenseOrder(nextExpenses, expenses[fromIndex]?.bill_id || null);
   }
 
-  function moveControlsFor(expense, index) {
+  function moveControlsFor(expense: SummaryExpense, index: number): ExpenseMoveControls {
     return {
       enabled: reorderEnabled,
       moving: movingBillId === expense.bill_id,
@@ -373,13 +445,13 @@ export default function SummaryPage() {
     };
   }
 
-  function dragPropsFor(expense, index) {
+  function dragPropsFor(expense: SummaryExpense, index: number): ExpenseDragProps {
     if (!reorderEnabled) return { draggable: false };
     return {
       draggable: true,
       isDragging: draggingId === expense.bill_id,
       isDropTarget: dropTargetId === expense.bill_id && draggingId !== expense.bill_id,
-      onDragStart: (event) => {
+      onDragStart: (event: DragEvent<HTMLDivElement>) => {
         setDraggingId(expense.bill_id);
         event.dataTransfer.effectAllowed = 'move';
         event.dataTransfer.setData('text/plain', String(expense.bill_id));
@@ -387,12 +459,12 @@ export default function SummaryPage() {
       onDragEnter: () => {
         if (draggingId && draggingId !== expense.bill_id) setDropTargetId(expense.bill_id);
       },
-      onDragOver: (event) => {
+      onDragOver: (event: DragEvent<HTMLDivElement>) => {
         event.preventDefault();
         event.dataTransfer.dropEffect = 'move';
         if (draggingId && draggingId !== expense.bill_id) setDropTargetId(expense.bill_id);
       },
-      onDrop: (event) => {
+      onDrop: (event: DragEvent<HTMLDivElement>) => {
         event.preventDefault();
         const sourceId = Number(event.dataTransfer.getData('text/plain') || draggingId);
         const fromIndex = expenses.findIndex(item => item.bill_id === sourceId);
@@ -551,33 +623,15 @@ export default function SummaryPage() {
                   <div className="summary-income-form grid gap-3 rounded-2xl border border-border/60 bg-background/80 p-3 md:grid-cols-[1fr_1fr_1fr_auto] md:items-end">
                     <label className="space-y-1">
                       <span className="text-xs font-medium text-muted-foreground">1st</span>
-                      <Input
-                        type="number"
-                        min="0"
-                        step="0.01"
-                        value={startingFirst}
-                        onChange={event => setStartingFirst(event.target.value)}
-                      />
+                      <Input type="number" min="0" step="0.01" value={startingFirst} onChange={event => setStartingFirst(event.target.value)} />
                     </label>
                     <label className="space-y-1">
                       <span className="text-xs font-medium text-muted-foreground">15th</span>
-                      <Input
-                        type="number"
-                        min="0"
-                        step="0.01"
-                        value={startingFifteenth}
-                        onChange={event => setStartingFifteenth(event.target.value)}
-                      />
+                      <Input type="number" min="0" step="0.01" value={startingFifteenth} onChange={event => setStartingFifteenth(event.target.value)} />
                     </label>
                     <label className="space-y-1">
                       <span className="text-xs font-medium text-muted-foreground">Other</span>
-                      <Input
-                        type="number"
-                        min="0"
-                        step="0.01"
-                        value={startingOther}
-                        onChange={event => setStartingOther(event.target.value)}
-                      />
+                      <Input type="number" min="0" step="0.01" value={startingOther} onChange={event => setStartingOther(event.target.value)} />
                     </label>
                     <Button onClick={saveStartingAmounts} disabled={saving} className="summary-edit-actions w-full md:w-auto">
                       {saving ? <Loader2 className="h-4 w-4 animate-spin" /> : <Save className="h-4 w-4" />}
@@ -612,8 +666,8 @@ export default function SummaryPage() {
                   {Number(data?.income?.amount) > 0 && Number(summary?.expense_total) > 0 && (
                     <div className="text-right">
                       <div className="text-xs text-muted-foreground">After expenses</div>
-                      <div className={cn('tracker-number mt-1 text-lg font-bold', moneyClass(Number(data.income.amount) - Number(summary.expense_total)))}>
-                        {fmt(Number(data.income.amount) - Number(summary.expense_total))}
+                      <div className={cn('tracker-number mt-1 text-lg font-bold', moneyClass(Number(data?.income?.amount) - Number(summary?.expense_total)))}>
+                        {fmt(Number(data?.income?.amount) - Number(summary?.expense_total))}
                       </div>
                     </div>
                   )}
@@ -623,12 +677,7 @@ export default function SummaryPage() {
                   <div className="grid gap-3 rounded-2xl border border-border/60 bg-background/80 p-3 md:grid-cols-[1fr_2fr_auto] md:items-end">
                     <label className="space-y-1">
                       <span className="text-xs font-medium text-muted-foreground">Label</span>
-                      <Input
-                        value={incomeLabel}
-                        onChange={e => setIncomeLabel(e.target.value)}
-                        placeholder="Salary"
-                        maxLength={80}
-                      />
+                      <Input value={incomeLabel} onChange={e => setIncomeLabel(e.target.value)} placeholder="Salary" maxLength={80} />
                     </label>
                     <label className="space-y-1">
                       <span className="text-xs font-medium text-muted-foreground">Amount</span>