Add one-off next check number override

Pencil button next to "Next check: X" in the header opens a modal
with a warning about sequence gaps/duplicates. Saves via new
PUT /api/account/:id/check-no endpoint (sets current_check_no = next - 1).

public/css/style.css

@@ -64,6 +64,26 @@ header {
   line-height: 1.4;
 }
 .btn-header-icon:hover { background: rgba(255,255,255,0.28); }
+.btn-header-inline {
+  background: none;
+  border: none;
+  color: rgba(255,255,255,0.5);
+  font-size: 11px;
+  cursor: pointer;
+  padding: 0 0 0 4px;
+  line-height: 1;
+  vertical-align: middle;
+}
+.btn-header-inline:hover { color: #fff; }
+.warning-box {
+  background: #fef9c3;
+  border: 1px solid #ca8a04;
+  border-radius: 4px;
+  padding: 10px 12px;
+  font-size: 12px;
+  color: #713f12;
+  line-height: 1.5;
+}
 
 /* ── Toolbar ── */
 .toolbar {

public/index.html

@@ -13,7 +13,7 @@
       <select id="account-switcher" class="account-switcher" title="Switch account"></select>
       <button id="btn-account-settings" class="btn-header-icon" title="Account settings">⚙</button>
     </div>
-    <span class="header-info">Next check: <strong id="current-check-no">—</strong></span>
+    <span class="header-info">Next check: <strong id="current-check-no">—</strong><button id="btn-set-check-no" class="btn-header-inline" title="Set next check number">✎</button></span>
   </header>
 
   <!-- View nav tabs -->
@@ -383,6 +383,29 @@
     </div>
   </div>
 
+  <!-- Set next check number modal -->
+  <div id="set-check-no-overlay" class="modal-overlay"></div>
+  <div id="set-check-no-modal" class="modal" role="dialog" aria-labelledby="set-check-no-title">
+    <div class="modal-header">
+      <h2 id="set-check-no-title">Set Next Check Number</h2>
+      <button id="btn-close-set-check-no" class="btn-icon" title="Close">×</button>
+    </div>
+    <div class="modal-body">
+      <div class="warning-box">
+        <strong>Warning:</strong> Changing the next check number can create duplicate check numbers or gaps in your sequence. Only do this if checks were printed outside this system or your book was restarted.
+      </div>
+      <div class="form-group" style="margin-top:12px">
+        <label for="set-check-no-input">Next check number</label>
+        <input type="number" id="set-check-no-input" min="1" step="1" style="width:120px">
+      </div>
+      <div id="set-check-no-error" class="wizard-error" hidden></div>
+    </div>
+    <div class="modal-footer">
+      <button id="btn-confirm-set-check-no" class="btn-primary">Set Number</button>
+      <button id="btn-cancel-set-check-no" class="btn-ghost">Cancel</button>
+    </div>
+  </div>
+
   <!-- Deposit slide-in panel -->
   <div id="dep-panel-overlay"></div>
   <aside id="deposit-panel">

public/js/app.js

@@ -642,6 +642,49 @@ async function saveAccountSettings() {
   }
 }
 
+// ── Set next check number ─────────────────────────────────────────────────────
+
+function openSetCheckNo() {
+  const current = state.account ? state.account.current_check_no + 1 : 1;
+  document.getElementById('set-check-no-input').value = current;
+  document.getElementById('set-check-no-error').hidden = true;
+  document.getElementById('set-check-no-overlay').classList.add('open');
+  document.getElementById('set-check-no-modal').classList.add('open');
+  document.getElementById('set-check-no-input').focus();
+  document.getElementById('set-check-no-input').select();
+}
+
+function closeSetCheckNo() {
+  document.getElementById('set-check-no-overlay').classList.remove('open');
+  document.getElementById('set-check-no-modal').classList.remove('open');
+}
+
+async function saveSetCheckNo() {
+  const errEl = document.getElementById('set-check-no-error');
+  const input = document.getElementById('set-check-no-input');
+  const next = parseInt(input.value, 10);
+  if (isNaN(next) || next < 1) {
+    errEl.textContent = 'Enter a valid check number (1 or higher).';
+    errEl.hidden = false;
+    return;
+  }
+  const btn = document.getElementById('btn-confirm-set-check-no');
+  btn.disabled = true;
+  btn.textContent = 'Saving…';
+  try {
+    await apiFetch('PUT', `/api/account/${state.activeAccountId}/check-no`, { next_check_no: next });
+    state.account.current_check_no = next - 1;
+    renderHeader();
+    closeSetCheckNo();
+  } catch (err) {
+    errEl.textContent = err.message;
+    errEl.hidden = false;
+  } finally {
+    btn.disabled = false;
+    btn.textContent = 'Set Number';
+  }
+}
+
 // ── Deposits ─────────────────────────────────────────────────────────────────
 
 const depState = {
@@ -1013,6 +1056,16 @@ function init() {
   document.getElementById('btn-cancel-acct-settings').addEventListener('click', closeAccountSettings);
   document.getElementById('acct-settings-overlay').addEventListener('click', closeAccountSettings);
   document.getElementById('btn-save-acct-settings').addEventListener('click', saveAccountSettings);
+
+  document.getElementById('btn-set-check-no').addEventListener('click', openSetCheckNo);
+  document.getElementById('btn-close-set-check-no').addEventListener('click', closeSetCheckNo);
+  document.getElementById('btn-cancel-set-check-no').addEventListener('click', closeSetCheckNo);
+  document.getElementById('set-check-no-overlay').addEventListener('click', closeSetCheckNo);
+  document.getElementById('btn-confirm-set-check-no').addEventListener('click', saveSetCheckNo);
+  document.getElementById('set-check-no-input').addEventListener('keydown', e => {
+    if (e.key === 'Enter') saveSetCheckNo();
+    if (e.key === 'Escape') closeSetCheckNo();
+  });
   document.getElementById('as-logo').addEventListener('change', e => {
     const file = e.target.files[0];
     if (!file) { acctSettings.logoData = null; return; }

src/app.js

@@ -84,6 +84,24 @@ app.get('/api/account/:id', (req, res) => {
   res.json(account);
 });
 
+// PUT /api/account/:id/check-no - override the next check number
+app.put('/api/account/:id/check-no', (req, res) => {
+  const db = require('./db/database');
+  const account = db.prepare('SELECT id FROM account WHERE id = ?').get(req.params.id);
+  if (!account) return res.status(404).json({ error: 'Account not found.' });
+
+  const next = parseInt(req.body.next_check_no, 10);
+  if (isNaN(next) || next < 1) {
+    return res.status(400).json({ error: 'Next check number must be a positive integer.' });
+  }
+
+  // current_check_no is the last-used number; next check will be current_check_no + 1
+  db.prepare("UPDATE account SET current_check_no = ?, updated_at = datetime('now') WHERE id = ?")
+    .run(next - 1, req.params.id);
+
+  res.json({ next_check_no: next });
+});
+
 // POST /api/account/setup - create a new account (wizard)
 app.post('/api/account/setup', (req, res) => {
   const db = require('./db/database');