feat(money): migrate services to cent-exact money.js helpers (batch 0.38.3)

FUTURE.md

@@ -31,6 +31,29 @@ Items are grouped under their priority section heading (`## 🔴 CRITICAL`, `##
 
 ## Pending Recommendations
 
+## 🟠 HIGH
+
+### 🟠 Cents Migration Stage 2 — Schema Flip to Integer Cents — HIGH
+**Priority:** HIGH
+**Added:** 2026-06-10 by Claude (cents migration stage 1)
+
+**Description:**
+Stage 1 is shipped: `utils/money.js` exists and all server-side money summation/
+rounding is cent-exact. Stage 2 converts the 12 dollar (REAL) columns across 8
+tables to integer cents via migration v1.03 and updates all ~288 query sites.
+
+**Scope:**
+- Apply v1.03 migration + rollback + schema.sql changes per `docs/cents-migration-plan.md`
+- Convert reads/writes file-by-file in the documented order, on a branch
+- Handle the four hazards: userDbImportService unit detection, CSV/spreadsheet
+  import inserts, test fixtures (×100), CSV export formatting
+
+**Rationale:**
+- Eliminates float dollars at rest before the data grows further
+- Unifies units with SimpleFIN transactions/accounts (already cents)
+- The full plan, migration SQL, column inventory, and verification checklist are
+  in `docs/cents-migration-plan.md` — this item is execution only
+
 ## 🟡 MEDIUM
 
 ### 🟡 Projected Cash Flow — MEDIUM

docs/cents-migration-plan.md

@@ -0,0 +1,124 @@
+# Cents Migration Plan (v1.03) — dollars (REAL) → integer cents
+
+**Status:** Stage 1 shipped (2026-06-10). Stage 2 (schema flip) NOT yet applied.
+**Stage 1 (done):** `utils/money.js` cents-core module; every float summation/rounding
+site in services/routes now uses `roundMoney` / `sumMoney` / `mulMoney` (cent-exact).
+**Stage 2 (this document):** flip storage and compute to integer cents.
+
+## Why staged
+
+The schema flip and the code conversion must land **atomically** — migrations run
+automatically at boot, so flipping storage with any of the ~288 query sites still
+assuming dollars corrupts data 100× on write or displays garbage on read. Stage 2
+should be done on a branch, file by file, with the checklist below.
+
+## Target architecture
+
+- **DB:** integer cents in all money columns (matches SimpleFIN `transactions` /
+  `financial_accounts`, which are already cents).
+- **Services:** compute in cents end-to-end.
+- **API:** keeps returning dollars (convert at route serialization, parse at input).
+  This keeps the web client (142 money sites) and the mobile app untouched.
+
+## Column inventory (12 columns, 8 tables)
+
+| Table | Columns (currently dollars REAL) |
+|---|---|
+| bills | expected_amount, current_balance, minimum_payment |
+| payments | amount, balance_delta |
+| monthly_bill_state | actual_amount |
+| monthly_starting_amounts | first_amount, fifteenth_amount, other_amount |
+| monthly_income | amount |
+| spending_budgets | amount |
+| snowball_plans | extra_payment |
+| users | snowball_extra_payment |
+
+NOT migrated: `bills.interest_rate` (a percentage), `transactions.amount`,
+`financial_accounts.balance/available_balance` (already cents).
+
+## v1.03 migration (add to the `migrations` array in db/database.js)
+
+```js
+{
+  version: 'v1.03',
+  description: 'money columns: dollars (REAL) → integer cents',
+  run() {
+    const conv = [
+      ['bills', ['expected_amount', 'current_balance', 'minimum_payment']],
+      ['payments', ['amount', 'balance_delta']],
+      ['monthly_bill_state', ['actual_amount']],
+      ['monthly_starting_amounts', ['first_amount', 'fifteenth_amount', 'other_amount']],
+      ['monthly_income', ['amount']],
+      ['spending_budgets', ['amount']],
+      ['snowball_plans', ['extra_payment']],
+      ['users', ['snowball_extra_payment']],
+    ];
+    for (const [table, cols] of conv) {
+      for (const col of cols) {
+        db.exec(`UPDATE ${table} SET ${col} = CAST(ROUND(${col} * 100) AS INTEGER) WHERE ${col} IS NOT NULL`);
+      }
+    }
+    console.log('[v1.03] money columns converted to integer cents');
+  }
+}
+```
+
+Notes:
+- SQLite affinity: existing columns stay declared REAL but hold integer values —
+  exact in both SQLite and JS (integers < 2^53). No table rebuild needed.
+- `db/schema.sql` must change the same columns to `INTEGER` + `-- cents` comments
+  so fresh installs are born in cents (v1.03 then no-ops on zero rows).
+- Registration: only the `runMigrations()` array matters. (The
+  reconcileLegacyMigrations sync assertion never fires — it runs before
+  `_runMigrationVersions` is populated; initSchema calls handleLegacyDatabase
+  before runMigrations. Worth fixing while in there.)
+- `ROLLBACK_SQL_MAP` entry: same loop with `ROUND(${col} / 100.0, 2)`.
+
+## Code conversion rules (stage 2)
+
+1. **Reads:** anything selecting the 12 columns now yields cents. Services treat
+   them as cents; `roundMoney(x)` calls on these values become `Math.round`, and
+   most add/subtract/compare logic is unit-consistent and needs no change.
+2. **Writes:** route input parsing converts dollars → `toCents()` once, at
+   validation (`validateBillData`, `validatePaymentInput`, monthly-state,
+   starting-amounts, budgets, snowball routes).
+3. **API output:** every `res.json` carrying money fields converts with
+   `fromCents()` — add per-entity serializers (`serializeBill`, `serializePayment`,
+   ...) in services and use them in routes instead of spreading raw rows.
+4. **Unification wins:** existing `cents → dollars` bridges disappear, e.g.
+   `Math.round(Math.abs(tx.amount)) / 100` in routes/matches.js and
+   `dollarsFromTransactionAmount()` in subscriptionService — payments and
+   transactions will finally share units.
+5. **Interest math:** `mulMoney` equivalents work directly in cents:
+   `Math.round(balanceCents * rate / 100 / 12)`.
+
+## Query-site inventory (grep `(FROM|INTO|UPDATE) <table>`, server-side)
+
+bills: 127 · payments: 108 · monthly_bill_state: 18 · snowball_plans: 20 ·
+monthly_starting_amounts: 7 · spending_budgets: 6 · monthly_income: 2
+
+Suggested file order (leaf → hub): paymentValidation → billsService →
+paymentAccountingService → statusService → trackerService → routes/payments →
+routes/bills → snowball/apr → analytics/spending/summary → subscription →
+import/export → notification/calendarFeed.
+
+## Hazards (each needs explicit handling)
+
+- **services/userDbImportService.js** copies raw numeric values from uploaded DBs
+  (lines ~152-219). After v1.03 it MUST check the source DB's `schema_migrations`
+  for v1.03: present → copy as-is; absent → `toCents()` each money field.
+- **Spreadsheet/CSV imports** (`spreadsheetImportService`, `csvTransactionImportService`)
+  parse user dollars — convert at their INSERT statements.
+- **Backups/restore:** safe automatically — restore swaps the file, `closeDb()` →
+  `getDb()` re-runs migrations, so pre-v1.03 backups get converted at next init.
+- **Tests:** ~67 money assertions/fixtures insert dollars via raw SQL — multiply
+  fixtures and expectations by 100 where they touch the 12 columns.
+- **export.js CSV:** `toFixed(2)` on dollars becomes `formatCentsUSD`/`fromCents`.
+
+## Verification before merging stage 2
+
+1. `npm run check:server && npm test` (after fixture updates).
+2. Invariant script: snapshot `SUM(col)` per money column pre-migration; assert
+   post-migration `SUM(col) / 100` matches to the cent.
+3. Manual pass: tracker totals, snowball projection, calendar summary, CSV export
+   against a copy of the production DB (`backups/` has real snapshots to test with).

routes/bills.js

@@ -22,6 +22,7 @@ const {
   applyBankPaymentAsSourceOfTruth,
 } = require('../services/paymentAccountingService');
 const { localDateString, todayLocal } = require('../utils/dates');
+const { roundMoney, sumMoney } = require('../utils/money');
 
 // ── GET /api/bills ────────────────────────────────────────────────────────────
 router.get('/', (req, res) => {
@@ -701,7 +702,7 @@ router.post('/:id/toggle-paid', (req, res) => {
     if (currentPayment.balance_delta != null) {
       const freshBill = db.prepare('SELECT current_balance FROM bills WHERE id = ?').get(billId);
       if (freshBill?.current_balance != null) {
-        const restored = Math.max(0, Math.round((freshBill.current_balance - currentPayment.balance_delta) * 100) / 100);
+        const restored = Math.max(0, roundMoney(freshBill.current_balance - currentPayment.balance_delta));
         db.prepare("UPDATE bills SET current_balance = ?, updated_at = datetime('now') WHERE id = ?").run(restored, billId);
       }
     }
@@ -922,8 +923,8 @@ router.get('/:id/amortization', (req, res) => {
     schedule,
     summary: {
       months:          schedule.length,
-      total_interest:  Math.round(total_interest * 100) / 100,
+      total_interest:  roundMoney(total_interest),
-      total_paid:      Math.round((schedule.reduce((s, r) => s + r.payment, 0)) * 100) / 100,
+      total_paid:      sumMoney(schedule, r => r.payment),
       capped:          schedule.length >= maxMonths && schedule[schedule.length - 1]?.balance > 0,
     },
     apr_snapshot,
@@ -964,7 +965,7 @@ router.patch('/:id/balance', (req, res) => {
     if (!Number.isFinite(val) || val < 0) {
       return res.status(400).json(standardizeError('current_balance must be a non-negative number', 'VALIDATION_ERROR', 'current_balance'));
     }
-    val = Math.round(val * 100) / 100;
+    val = roundMoney(val);
   }
 
   db.prepare("UPDATE bills SET current_balance = ?, updated_at = datetime('now') WHERE id = ?").run(val, billId);

routes/calendar.js

@@ -14,6 +14,7 @@ const {
   revokeToken,
 } = require('../services/calendarFeedService');
 const { localDateString } = require('../utils/dates');
+const { roundMoney, sumMoney } = require('../utils/money');
 
 function clampDay(year, month, day) {
   const daysInMonth = new Date(year, month, 0).getDate();
@@ -225,11 +226,17 @@ router.get('/', (req, res) => {
   }
 
   const activeBills = calendarBills.filter(bill => !bill.is_skipped);
-  const expectedTotal = activeBills.reduce((sum, bill) => sum + (bill.effective_amount || 0), 0);
+  const expectedTotal = sumMoney(activeBills, bill => bill.effective_amount || 0);
-  const paidTotal = activeBills.reduce((sum, bill) => sum + (bill.paid_amount || 0), 0);
+  const paidTotal = sumMoney(activeBills, bill => bill.paid_amount || 0);
-  const remainingTotal = Math.max(0, expectedTotal - paidTotal);
+  const remainingTotal = Math.max(0, roundMoney(expectedTotal - paidTotal));
   const paidPercent = expectedTotal > 0 ? Math.min(100, Math.round((paidTotal / expectedTotal) * 100)) : 0;
 
+  // Cent-exact: the per-day loops above accumulate floats; settle them here.
+  for (const day of days) {
+    day.status_summary.total_paid = roundMoney(day.status_summary.total_paid);
+    day.status_summary.total_due  = roundMoney(day.status_summary.total_due);
+  }
+
   res.json({
     year,
     month,

routes/transactions.js

@@ -15,6 +15,7 @@ const {
 } = require('../services/transactionMatchService');
 const { reactivatePaymentsOverriddenBy } = require('../services/paymentAccountingService');
 const { todayLocal } = require('../utils/dates');
+const { roundMoney } = require('../utils/money');
 
 const MATCH_STATUSES = new Set(['unmatched', 'matched', 'ignored']);
 const SOURCE_TYPES = new Set(['manual', 'file_import', 'provider_sync']);
@@ -573,7 +574,7 @@ router.post('/unmatch-bulk', (req, res) => {
             if (!payment.accounting_excluded && payment.balance_delta != null) {
               const bill = db.prepare('SELECT current_balance FROM bills WHERE id = ?').get(payment.bill_id);
               if (bill?.current_balance != null) {
-                const restored = Math.max(0, Math.round((Number(bill.current_balance) - Number(payment.balance_delta)) * 100) / 100);
+                const restored = Math.max(0, roundMoney(Number(bill.current_balance) - Number(payment.balance_delta)));
                 db.prepare(`
                   UPDATE bills
                   SET current_balance        = ?,

services/amountSuggestionService.js

@@ -1,6 +1,7 @@
 'use strict';
 
 const { accountingActiveSql } = require('./paymentAccountingService');
+const { roundMoney } = require('../utils/money');
 
 /**
  * Computes a suggested expected amount for a bill based on the rolling median
@@ -47,7 +48,7 @@ function computeAmountSuggestion(db, billId, year, month) {
     : sorted[mid];
 
   return {
-    suggestion: Math.round(median * 100) / 100,
+    suggestion: roundMoney(median),
     months_used: amounts.length,
     confidence: amounts.length >= 3 ? 'high' : 'low',
   };

services/analyticsService.js

@@ -2,6 +2,7 @@
 
 const { getDb } = require('../db/database');
 const { accountingActiveSql } = require('./paymentAccountingService');
+const { sumMoney } = require('../utils/money');
 
 function parseInteger(value, fallback) {
   if (value === undefined || value === null || value === '') return fallback;
@@ -181,7 +182,7 @@ function getAnalyticsSummary(userId, query = {}) {
   const stateByBillMonth = new Map(stateRows.map(row => [`${row.bill_id}:${monthKey(row.year, row.month)}`, row]));
 
   const monthly_spending = rangeMonths.map(m => {
-    const total = bills.reduce((sum, bill) => sum + (paymentByBillMonth.get(`${bill.id}:${m.key}`) || 0), 0);
+    const total = sumMoney(bills, bill => paymentByBillMonth.get(`${bill.id}:${m.key}`) || 0);
     return { month: m.key, label: m.label, total: Number(total.toFixed(2)) };
   }).filter(row => row.total > 0);
 

services/aprService.js

@@ -1,3 +1,5 @@
+
+const { roundMoney, sumMoney } = require('../utils/money');
 /**
  * APR / amortization mathematics.
  * All functions are pure — no DB access, no side effects.
@@ -192,7 +194,7 @@ function calculateMinimumOnly(debts, startDate = new Date()) {
   }));
 
   const maxMonth      = Math.max(0, ...active.map(d => d.payoffMonth || 0));
-  const totalInterest = active.reduce((s, d) => s + d.totalInterest, 0);
+  const totalInterest = sumMoney(active, d => d.totalInterest);
 
   return {
     months_to_freedom:   maxMonth || null,
@@ -237,7 +239,7 @@ function debtAprSnapshot(bill) {
 // ── Helpers ───────────────────────────────────────────────────────────────────
 
 function round2(n) {
-  return Math.round(n * 100) / 100;
+  return roundMoney(n);
 }
 
 module.exports = {

services/billsService.js

@@ -1,4 +1,5 @@
 const { monthKey } = require('../utils/dates');
+const { roundMoney, mulMoney } = require('../utils/money');
 const VALID_VISIBILITY = ['default', 'all', 'ranges', 'none'];
 
 const TEMPLATE_FIELDS = [
@@ -481,11 +482,11 @@ function computeBalanceDelta(bill, paymentAmount) {
 
   const currentMonth  = monthKey(); // "YYYY-MM" (local time)
   const applyInterest = rate > 0 && bill.interest_accrued_month !== currentMonth;
-  const interestDelta = applyInterest ? Math.round(bal * (rate / 100 / 12) * 100) / 100 : 0;
+  const interestDelta = applyInterest ? mulMoney(bal, rate / 100 / 12) : 0;
 
   const raw        = bal + interestDelta - amt;
-  const newBalance = Math.round(Math.max(0, raw) * 100) / 100;
+  const newBalance = roundMoney(Math.max(0, raw));
-  const delta      = Math.round((newBalance - bal) * 100) / 100;
+  const delta      = roundMoney(newBalance - bal);
 
   return {
     new_balance:            newBalance,

services/driftService.js

@@ -5,6 +5,7 @@ const { getCycleRange } = require('./statusService');
 const { accountingActiveSql } = require('./paymentAccountingService');
 const { getUserSettings } = require('./userSettings');
 const { localDateString } = require('../utils/dates');
+const { roundMoney } = require('../utils/money');
 
 const MONTHS_BACK  = 3;
 const MIN_PAID_MONTHS = 2;
@@ -91,7 +92,7 @@ function getDriftReport(userId, now = new Date()) {
         name:             bill.name,
         category_name:    bill.category_name ?? null,
         expected_amount:  bill.expected_amount,
-        recent_amount:    Math.round(recentAmount * 100) / 100,
+        recent_amount:    roundMoney(recentAmount),
         drift_pct:        Math.round(driftPct * 10) / 10,
         direction:        delta > 0 ? 'up' : 'down',
         months_sampled:   monthTotals.length,

services/paymentAccountingService.js

@@ -2,6 +2,7 @@
 
 const { computeBalanceDelta, applyBalanceDelta } = require('./billsService');
 const { getCycleRange } = require('./statusService');
+const { roundMoney } = require('../utils/money');
 
 const ACCOUNTING_ACTIVE_SQL = 'COALESCE(accounting_excluded, 0) = 0';
 const BANK_PAYMENT_SOURCES = new Set(['provider_sync', 'transaction_match', 'auto_match']);
@@ -39,7 +40,7 @@ function reversePaymentBalance(db, payment) {
   const bill = db.prepare('SELECT id, current_balance FROM bills WHERE id = ?').get(payment.bill_id);
   if (bill?.current_balance == null) return;
 
-  const restored = Math.max(0, Math.round((Number(bill.current_balance) - Number(payment.balance_delta)) * 100) / 100);
+  const restored = Math.max(0, roundMoney(Number(bill.current_balance) - Number(payment.balance_delta)));
   db.prepare(`
     UPDATE bills
     SET current_balance        = ?,

services/snowballService.js

@@ -1,3 +1,5 @@
+
+const { roundMoney, sumMoney } = require('../utils/money');
 /**
  * Debt payoff calculators — Snowball and Avalanche methods.
  *
@@ -112,7 +114,7 @@ function _simulate(orderedDebts, extraPayment, startDate) {
   }));
 
   const maxMonth      = Math.max(0, ...active.map(d => d.payoffMonth || 0));
-  const totalInterest = active.reduce((s, d) => s + d.totalInterest, 0);
+  const totalInterest = sumMoney(active, d => d.totalInterest);
 
   return {
     months_to_freedom:   maxMonth || null,
@@ -152,7 +154,7 @@ function calculateAvalanche(debts, extraPayment = 0, startDate = new Date()) {
 }
 
 function round2(n) {
-  return Math.round(n * 100) / 100;
+  return roundMoney(n);
 }
 
 module.exports = { calculateSnowball, calculateAvalanche };

services/statusService.js

@@ -21,9 +21,7 @@ function pad(value) {
   return String(value).padStart(2, '0');
 }
 
-function roundMoney(value) {
+const { roundMoney, sumMoney } = require('../utils/money');
-  return Math.round((Number(value) || 0) * 100) / 100;
-}
 
 function dateString(year, month, day) {
   return `${year}-${pad(month)}-${pad(day)}`;
@@ -196,7 +194,7 @@ function calculateStatus(bill, payments, dueDate, today, options = {}) {
   const gracePeriodDays = resolveGracePeriodDays(options.gracePeriodDays);
   const safePayments = Array.isArray(payments) ? payments : [];
   const expectedAmount = Number(bill.expected_amount) || 0;
-  const totalPaid = roundMoney(safePayments.reduce((sum, p) => sum + (Number(p.amount) || 0), 0));
+  const totalPaid = sumMoney(safePayments, p => p.amount);
 
   if (totalPaid >= expectedAmount) return 'paid';
 
@@ -225,7 +223,7 @@ function buildTrackerRow(bill, payments, year, month, todayStr, options = {}) {
   const safePayments = Array.isArray(payments) ? payments : [];
   const status = calculateStatus(bill, safePayments, dueDate, todayStr, options);
   const expectedAmount = Number(bill.expected_amount) || 0;
-  const totalPaid = roundMoney(safePayments.reduce((sum, p) => sum + (Number(p.amount) || 0), 0));
+  const totalPaid = sumMoney(safePayments, p => p.amount);
   const hasPayment = safePayments.length > 0;
   const isSettled = status === 'paid' || status === 'autodraft';
   const paidTowardDue = roundMoney(Math.min(totalPaid, expectedAmount));

services/subscriptionService.js

@@ -2,6 +2,7 @@
 
 const { billingCycleForCycleType, insertBill, validateBillData } = require('./billsService');
 const { localDateString, todayLocal } = require('../utils/dates');
+const { roundMoney, sumMoney, mulMoney } = require('../utils/money');
 
 const SUBSCRIPTION_TYPES = [
   'streaming', 'software', 'cloud', 'music', 'news',
@@ -471,7 +472,7 @@ function monthlyEquivalent(amount, cycleType, billingCycle) {
     ? 'annual'
     : key;
   const factor = MONTHLY_FACTORS[key] ?? MONTHLY_FACTORS[fallback] ?? 1;
-  return Math.round(Number(amount || 0) * factor * 100) / 100;
+  return mulMoney(Number(amount || 0), factor);
 }
 
 function nextDueDate(bill, now = new Date()) {
@@ -499,7 +500,7 @@ function decorateSubscription(bill) {
     is_subscription: !!bill.is_subscription,
     active: !!bill.active,
     monthly_equivalent: monthly,
-    yearly_equivalent: Math.round(monthly * 12 * 100) / 100,
+    yearly_equivalent: mulMoney(monthly, 12),
     next_due_date: nextDueDate(bill),
     subscription_type: bill.subscription_type || inferType(`${bill.name} ${bill.category_name || ''}`, null),
   };
@@ -529,7 +530,7 @@ function getSubscriptions(db, userId) {
 
 function getSubscriptionSummary(subscriptions) {
   const active = subscriptions.filter(item => item.active);
-  const monthlyTotal = active.reduce((sum, item) => sum + Number(item.monthly_equivalent || 0), 0);
+  const monthlyTotal = sumMoney(active, item => item.monthly_equivalent);
   const typeTotals = new Map();
   for (const item of active) {
     const type = item.subscription_type || 'other';
@@ -539,9 +540,9 @@ function getSubscriptionSummary(subscriptions) {
   return {
     active_count: active.length,
     paused_count: subscriptions.length - active.length,
-    monthly_total: Math.round(monthlyTotal * 100) / 100,
+    monthly_total: roundMoney(monthlyTotal),
-    yearly_total: Math.round(monthlyTotal * 12 * 100) / 100,
+    yearly_total: mulMoney(monthlyTotal, 12),
-    top_type: topType ? { type: topType[0], monthly_total: Math.round(topType[1] * 100) / 100 } : null,
+    top_type: topType ? { type: topType[0], monthly_total: roundMoney(topType[1]) } : null,
   };
 }
 
@@ -553,7 +554,7 @@ function existingBillNames(db, userId) {
 }
 
 function dollarsFromTransactionAmount(amount) {
-  return Math.round((Math.abs(Number(amount || 0)) / 100) * 100) / 100;
+  return roundMoney(Math.abs(Number(amount || 0)) / 100);
 }
 
 function recommendationAccountLabel(item) {
@@ -706,7 +707,7 @@ function existingBillMatch(existingBills, { merchant, catalogEntry, averageAmoun
         has_merchant_rule: !!bill.has_merchant_rule,
         score,
         strong: score >= 90 || (amountDelta !== null && amountDelta <= 1 && dueDelta <= 2),
-        amount_delta: amountDelta === null ? null : Math.round(amountDelta * 100) / 100,
+        amount_delta: amountDelta === null ? null : roundMoney(amountDelta),
         due_day_delta: dueDelta,
         reasons,
       };
@@ -800,7 +801,7 @@ function getSubscriptionRecommendations(db, userId) {
       .sort((a, b) => String(a.tx_date).localeCompare(String(b.tx_date)));
     if (sorted.length === 0) continue;
 
-    const averageAmount = sorted.reduce((sum, item) => sum + item.amount_dollars, 0) / sorted.length;
+    const averageAmount = sumMoney(sorted, item => item.amount_dollars) / sorted.length;
     const maxDelta = sorted.length > 1
       ? Math.max(...sorted.map(item => Math.abs(item.amount_dollars - averageAmount)))
       : 0;
@@ -914,7 +915,7 @@ function buildRecommendation({ merchant, catalogEntry, sorted, averageAmount, ma
     id: Buffer.from(`${merchant}:${Math.round(averageAmount)}:${last.tx_date}`).toString('base64url'),
     name,
     subscription_type: subscriptionType,
-    expected_amount: Math.round(averageAmount * 100) / 100,
+    expected_amount: roundMoney(averageAmount),
     monthly_equivalent: monthlyEquivalent(averageAmount, cycleType, cycleType),
     cycle_type: cycleType,
     billing_cycle: billingCycleForCycleType(cycleType),
@@ -943,7 +944,7 @@ function buildRecommendation({ merchant, catalogEntry, sorted, averageAmount, ma
       amount_range: sorted.length > 1 ? {
         min: Math.min(...sorted.map(item => item.amount_dollars)),
         max: Math.max(...sorted.map(item => item.amount_dollars)),
-        max_delta: Math.round(maxDelta * 100) / 100,
+        max_delta: roundMoney(maxDelta),
       } : null,
       ambiguity: ambiguityInfo ? {
         ambiguous: !!ambiguityInfo.ambiguous,

services/trackerService.js

@@ -8,6 +8,7 @@ const { computeAmountSuggestion } = require('./amountSuggestionService');
 const { accountingActiveSql } = require('./paymentAccountingService');
 const { normalizeMerchant } = require('./subscriptionService');
 const { localDateString } = require('../utils/dates');
+const { sumMoney } = require('../utils/money');
 
 const DEFAULT_PENDING_DAYS = 3;
 
@@ -392,7 +393,7 @@ function buildThreeMonthTrend(db, userId, year, month, end, currentMonthPaid) {
     });
   }
 
-  const threeMonthAvg = months.reduce((sum, m) => sum + m.payment, 0) / 3;
+  const threeMonthAvg = sumMoney(months, m => m.payment) / 3;
   let percentChange = 0;
   let direction = 'flat';
   if (threeMonthAvg > 0) {
@@ -478,8 +479,8 @@ function getTracker(userId, query = {}, now = new Date()) {
   const dayOfMonth = now.getDate();
   const activeRemainingPeriod = dayOfMonth < 15 ? '1st' : '15th';
   const periodRows = activeRows.filter(r => r.bucket === activeRemainingPeriod);
-  const periodPaidTowardDue = roundMoney(periodRows.reduce((s, r) => s + rowPaidTowardDue(r), 0));
+  const periodPaidTowardDue = sumMoney(periodRows, rowPaidTowardDue);
-  const periodOutstandingBalance = roundMoney(periodRows.reduce((s, r) => s + Math.max(r.balance || 0, 0), 0));
+  const periodOutstandingBalance = sumMoney(periodRows, r => Math.max(r.balance || 0, 0));
   const periodStartingAmount = activeRemainingPeriod === '1st'
     ? (startingAmounts?.first_amount || 0)
     : (startingAmounts?.fifteenth_amount || 0);
@@ -500,12 +501,12 @@ function getTracker(userId, query = {}, now = new Date()) {
   const periodEndDay   = activeRemainingPeriod === '1st' ? 14 : lastDayOfMonth;
   const periodEndLabel = `${['Jan','Feb','Mar','Apr','May','Jun','Jul','Aug','Sep','Oct','Nov','Dec'][month - 1]} ${periodEndDay}`;
 
-  const activeTotalPaid = roundMoney(activeRows.reduce((s, r) => s + r.total_paid, 0));
+  const activeTotalPaid = sumMoney(activeRows, r => r.total_paid);
-  const activePaidTowardDue = roundMoney(activeRows.reduce((s, r) => s + rowPaidTowardDue(r), 0));
+  const activePaidTowardDue = sumMoney(activeRows, rowPaidTowardDue);
-  const activeTotalExpected = roundMoney(activeRows.reduce((s, r) => s + rowDueAmount(r), 0));
+  const activeTotalExpected = sumMoney(activeRows, rowDueAmount);
-  const activeOutstandingBalance = roundMoney(activeRows.reduce((s, r) => s + Math.max(r.balance || 0, 0), 0));
+  const activeOutstandingBalance = sumMoney(activeRows, r => Math.max(r.balance || 0, 0));
 
-  const periodBillsTotal   = roundMoney(periodRows.reduce((s, r) => s + rowDueAmount(r), 0));
+  const periodBillsTotal   = sumMoney(periodRows, rowDueAmount);
   const periodPaidCount    = periodRows.filter(r => ['paid', 'autodraft'].includes(r.status)).length;
   const periodTotalCount   = periodRows.length;
 
@@ -538,10 +539,10 @@ function getTracker(userId, query = {}, now = new Date()) {
     month_total_count:  monthTotalCount,
     month_projected:    monthProjected,
   };
-  const totalOverdue = roundMoney(rows
+  const totalOverdue = sumMoney(
-    .filter(r => !r.is_skipped && (r.status === 'late' || r.status === 'missed'))
+    rows.filter(r => !r.is_skipped && (r.status === 'late' || r.status === 'missed')),
-    .reduce((s, r) => s + r.balance, 0));
+    r => r.balance);
-  const previousMonthTotal = roundMoney(activeRows.reduce((s, r) => s + r.previous_month_paid, 0));
+  const previousMonthTotal = sumMoney(activeRows, r => r.previous_month_paid);
 
   return {
     year,

services/transactionMatchService.js

@@ -10,6 +10,7 @@ const {
   decorateTransaction,
   getTransactionForUser,
 } = require('./transactionService');
+const { roundMoney } = require('../utils/money');
 
 const MATCH_PAYMENT_SOURCE = 'transaction_match';
 const MATCH_PAYMENT_METHOD = 'transaction_match';
@@ -108,7 +109,7 @@ function restorePaymentBalance(db, payment) {
   const bill = db.prepare('SELECT id, current_balance FROM bills WHERE id = ?').get(payment.bill_id);
   if (bill?.current_balance == null) return;
 
-  const restored = Math.max(0, Math.round((Number(bill.current_balance) - Number(payment.balance_delta)) * 100) / 100);
+  const restored = Math.max(0, roundMoney(Number(bill.current_balance) - Number(payment.balance_delta)));
   // Clear interest_accrued_month when reversing a payment that charged interest,
   // so the re-applied payment can accrue interest fresh.
   db.prepare(`