diff --git a/index.html b/index.html
index d3e0e66..1341657 100644
--- a/index.html
+++ b/index.html
@@ -6,6 +6,17 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <meta name="color-scheme" content="light dark" />
     <title>Voiced</title>
+    <script>
+      // Apply the last-used theme before first paint so a dark theme never flashes white.
+      (function () {
+        var t = "g10";
+        try {
+          t = localStorage.getItem("voiced.theme") === "g100" ? "g100" : "g10";
+        } catch (e) {}
+        document.documentElement.classList.add("cds--" + t);
+        document.documentElement.setAttribute("data-carbon-theme", t);
+      })();
+    </script>
   </head>
   <body>
     <div id="root"></div>
diff --git a/src/App.tsx b/src/App.tsx
index 6519700..4b158b0 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -11,6 +11,7 @@ import Clients from "./views/Clients";
 import { ToastProvider, useToast } from "./components/ToastProvider";
 import AppSettings from "./views/AppSettings";
 import { requestSettingsTab } from "./lib/settingsTab";
+import { applyDocumentTheme, cachedTheme, normalizeTheme } from "./lib/theme";
 
 export default function App() {
   return (
@@ -46,9 +47,15 @@ function AppInner() {
     void refreshSettings();
   }, [refreshSettings]);
 
+  // Before settings load (and on the error screen) use the cached theme so the window never flashes white.
+  const theme = settings ? normalizeTheme(settings.theme) : cachedTheme();
+  useEffect(() => {
+    applyDocumentTheme(theme);
+  }, [theme]);
+
   if (loading) {
     return (
-      <Theme theme="g10">
+      <Theme theme={theme} className="voiced-theme">
         <div className="voiced-empty">
           <Loading description="Loading Voiced" withOverlay={false} small />
         </div>
@@ -58,7 +65,7 @@ function AppInner() {
 
   if (error) {
     return (
-      <Theme theme="g10">
+      <Theme theme={theme} className="voiced-theme">
         <div className="voiced-page">
           <InlineNotification
             kind="error"
@@ -74,11 +81,9 @@ function AppInner() {
 
   if (!settings) return null;
 
-  const theme = settings.theme === "g100" ? "g100" : "g10";
-
   if (!settings.onboarded) {
     return (
-      <Theme theme={theme}>
+      <Theme theme={theme} className="voiced-theme">
         <Onboarding
           initial={settings}
           onDone={(next) => {
@@ -106,8 +111,8 @@ function AppInner() {
   };
 
   return (
-    <Theme theme={theme}>
-      <AppShell view={view} onNavigate={setView} theme={settings.theme} onToggleTheme={toggleTheme}>
+    <Theme theme={theme} className="voiced-theme">
+      <AppShell view={view} onNavigate={setView} theme={theme} onToggleTheme={toggleTheme}>
         {/* Main views stay mounted so a half-typed invoice survives switching tabs. */}
         <NewInvoice
           settings={settings}
@@ -116,6 +121,8 @@ function AppInner() {
           onActivate={() => setView("new")}
           openDraftId={openDraftId}
           onDraftOpened={() => setOpenDraftId(null)}
+          theme={theme}
+          onToggleTheme={toggleTheme}
         />
         <div hidden={view !== "invoices"}>
           <InvoiceHistory
diff --git a/src/components/AppShell.tsx b/src/components/AppShell.tsx
index 5b0a10b..02e0dd8 100644
--- a/src/components/AppShell.tsx
+++ b/src/components/AppShell.tsx
@@ -61,7 +61,11 @@ export function AppShell({ view, onNavigate, theme, onToggleTheme, children }: A
           ))}
         </HeaderNavigation>
         <HeaderGlobalBar>
-          <HeaderGlobalAction aria-label="Toggle colour theme" onClick={onToggleTheme}>
+          <HeaderGlobalAction
+            aria-label={theme === "g100" ? "Switch to light theme" : "Switch to dark theme"}
+            tooltipAlignment="end"
+            onClick={onToggleTheme}
+          >
             {theme === "g100" ? <Light size={20} /> : <Asleep size={20} />}
           </HeaderGlobalAction>
         </HeaderGlobalBar>
diff --git a/src/components/BankAccountModal.tsx b/src/components/BankAccountModal.tsx
new file mode 100644
index 0000000..e23ffc7
--- /dev/null
+++ b/src/components/BankAccountModal.tsx
@@ -0,0 +1,148 @@
+import { useEffect, useState, type RefObject } from "react";
+import { Column, Grid, Modal, TextInput, Toggle } from "@carbon/react";
+import { api } from "../lib/api";
+import type { BankAccount } from "../lib/types";
+import { ifscError } from "../lib/validators";
+import { useToast } from "./ToastProvider";
+
+export const blankBank = (): BankAccount => ({
+  id: null,
+  label: "",
+  bankName: "",
+  accountName: "",
+  accountNo: "",
+  branch: "",
+  ifsc: "",
+  isDefault: false,
+});
+
+interface BankAccountModalProps {
+  open: boolean;
+  /** The account to edit; null opens a blank one. */
+  bank: BankAccount | null;
+  onClose: () => void;
+  onSaved: (bank: BankAccount) => void;
+  /** Focus returns here when the modal closes. */
+  launcherRef?: RefObject<HTMLElement | null>;
+}
+
+export default function BankAccountModal({ open, bank, onClose, onSaved, launcherRef }: BankAccountModalProps) {
+  const toast = useToast();
+  const [form, setForm] = useState<BankAccount>(blankBank());
+  const [busy, setBusy] = useState(false);
+  const [touched, setTouched] = useState(false);
+
+  useEffect(() => {
+    if (!open) return;
+    setForm(bank ? { ...bank } : blankBank());
+    setBusy(false);
+    setTouched(false);
+  }, [open, bank]);
+
+  const set = <K extends keyof BankAccount>(key: K, value: BankAccount[K]) =>
+    setForm((prev) => ({ ...prev, [key]: value }));
+
+  const bankNameProblem = form.bankName.trim() ? undefined : "Bank name is required";
+  const accountNoProblem = form.accountNo.trim() ? undefined : "Account number is required";
+  const ifscProblem = ifscError(form.ifsc);
+  const blocking = bankNameProblem ?? accountNoProblem ?? ifscProblem;
+
+  const submit = async () => {
+    setTouched(true);
+    if (blocking) return;
+    setBusy(true);
+    try {
+      const saved = await api.saveBank({
+        ...form,
+        bankName: form.bankName.trim(),
+        accountNo: form.accountNo.trim(),
+        ifsc: form.ifsc.trim().toUpperCase(),
+      });
+      toast.success(form.id === null ? "Bank account added" : "Bank account saved", saved.bankName);
+      onSaved(saved);
+    } catch (e) {
+      toast.error("Could not save bank account", String(e));
+      setBusy(false);
+    }
+  };
+
+  return (
+    <Modal
+      open={open}
+      modalHeading={bank?.id ? "Edit bank account" : "New bank account"}
+      primaryButtonText={busy ? "Saving…" : "Save account"}
+      secondaryButtonText="Cancel"
+      primaryButtonDisabled={busy}
+      onRequestClose={onClose}
+      onRequestSubmit={() => void submit()}
+      launcherButtonRef={launcherRef}
+      size="md"
+    >
+      <Grid narrow>
+        <Column sm={4} md={4} lg={8}>
+          <TextInput
+            id="bm-label"
+            labelText="Label (optional)"
+            value={form.label}
+            onChange={(e) => set("label", e.target.value)}
+          />
+        </Column>
+        <Column sm={4} md={4} lg={8}>
+          <TextInput
+            id="bm-bankName"
+            labelText="Bank name"
+            value={form.bankName}
+            onChange={(e) => set("bankName", e.target.value)}
+            invalid={touched && Boolean(bankNameProblem)}
+            invalidText={bankNameProblem}
+            data-modal-primary-focus
+          />
+        </Column>
+        <Column sm={4} md={4} lg={8}>
+          <TextInput
+            id="bm-accountName"
+            labelText="Account name"
+            value={form.accountName}
+            onChange={(e) => set("accountName", e.target.value)}
+          />
+        </Column>
+        <Column sm={4} md={4} lg={8}>
+          <TextInput
+            id="bm-accountNo"
+            labelText="Account number"
+            value={form.accountNo}
+            onChange={(e) => set("accountNo", e.target.value)}
+            invalid={touched && Boolean(accountNoProblem)}
+            invalidText={accountNoProblem}
+          />
+        </Column>
+        <Column sm={4} md={4} lg={8}>
+          <TextInput
+            id="bm-branch"
+            labelText="Branch"
+            value={form.branch}
+            onChange={(e) => set("branch", e.target.value)}
+          />
+        </Column>
+        <Column sm={4} md={4} lg={8}>
+          <TextInput
+            id="bm-ifsc"
+            labelText="IFSC"
+            value={form.ifsc}
+            onChange={(e) => set("ifsc", e.target.value.toUpperCase())}
+            invalid={Boolean(ifscProblem)}
+            invalidText={ifscProblem}
+          />
+        </Column>
+        <Column sm={4} md={8} lg={16}>
+          <Toggle
+            id="bm-default"
+            labelText="Use as default account"
+            toggled={form.isDefault}
+            onToggle={(value) => set("isDefault", value)}
+          />
+        </Column>
+      </Grid>
+    </Modal>
+  );
+}
diff --git a/src/lib/theme.ts b/src/lib/theme.ts
new file mode 100644
index 0000000..20bcd19
--- /dev/null
+++ b/src/lib/theme.ts
@@ -0,0 +1,31 @@
+export type ThemeName = "g10" | "g100";
+
+const STORAGE_KEY = "voiced.theme";
+
+export const normalizeTheme = (value: string | null | undefined): ThemeName => (value === "g100" ? "g100" : "g10");
+
+/** The theme last applied on this machine; used before settings load so there is no light flash. */
+export function cachedTheme(): ThemeName {
+  try {
+    return normalizeTheme(localStorage.getItem(STORAGE_KEY));
+  } catch {
+    return "g10";
+  }
+}
+
+/**
+ * Puts the Carbon theme tokens on <html> as well as on the <Theme> zone, so the page canvas, the
+ * overscroll area and any window area below the content follow the chosen theme.
+ * index.html runs the same class switch before React mounts.
+ */
+export function applyDocumentTheme(theme: ThemeName): void {
+  const root = document.documentElement;
+  root.classList.remove("cds--g10", "cds--g100");
+  root.classList.add(`cds--${theme}`);
+  root.dataset.carbonTheme = theme;
+  try {
+    localStorage.setItem(STORAGE_KEY, theme);
+  } catch {
+    /* storage may be blocked; the class is already applied */
+  }
+}
diff --git a/src/styles/carbon.scss b/src/styles/carbon.scss
index 2ded577..1cfed4c 100644
--- a/src/styles/carbon.scss
+++ b/src/styles/carbon.scss
@@ -100,18 +100,49 @@
 }
 
 /* ---------- App shell ---------- */
-html,
-body,
-#root {
-  height: 100%;
+// The Carbon theme tokens are also set on <html> (see lib/theme.ts), so the canvas follows the theme
+// even where the <Theme> zone does not reach (below short content, overscroll, window resize).
+html {
+  min-height: 100%;
+  background-color: var(--cds-background);
+  color-scheme: light;
+}
+
+html.cds--g100 {
+  color-scheme: dark;
 }
 
 body {
   margin: 0;
+  min-height: 100vh;
+  min-height: 100dvh;
   background-color: var(--cds-background);
   color: var(--cds-text-primary);
 }
 
+#root {
+  min-height: 100vh;
+  min-height: 100dvh;
+  display: flex;
+  flex-direction: column;
+}
+
+// The theme zone fills the window, so the dark theme covers it entirely.
+.voiced-theme {
+  flex: 1 0 auto;
+  min-height: 100vh;
+  min-height: 100dvh;
+  background-color: var(--cds-background);
+  color: var(--cds-text-primary);
+}
+
+// Keep the header actions inside the window edges.
+.cds--header {
+  box-sizing: border-box;
+  max-width: 100vw;
+  padding-inline: 0.5rem;
+}
+
 .voiced-brand {
   display: flex;
   align-items: center;
diff --git a/src/views/AppSettings.tsx b/src/views/AppSettings.tsx
index fbca0b3..f691375 100644
--- a/src/views/AppSettings.tsx
+++ b/src/views/AppSettings.tsx
@@ -1,4 +1,4 @@
-import { useEffect, useState } from "react";
+import { useEffect, useRef, useState, type MouseEvent } from "react";
 import {
   Button,
   Column,
@@ -36,7 +36,7 @@ import {
   type Settings,
   type TaxType,
 } from "../lib/types";
-import { emailError, ifscError, panError, phoneError, vendorGstinError } from "../lib/validators";
+import { emailError, panError, phoneError, vendorGstinError } from "../lib/validators";
 import { ImagePicker } from "../components/ImagePicker";
 import { LogoBranding } from "../components/LogoBranding";
 import DataBackupPanel from "../components/DataBackupPanel";
@@ -45,19 +45,9 @@ import ErpnextSettingsPanel from "../components/ErpnextSettingsPanel";
 import { FontOverrideTable } from "../components/FontOverrideTable";
 import { useToast } from "../components/ToastProvider";
 import { SETTINGS_TABS, loadSettingsTab, saveSettingsTab } from "../lib/settingsTab";
+import BankAccountModal from "../components/BankAccountModal";
 import SeriesSettings from "./SeriesSettings";
 
-const blankBank = (): BankAccount => ({
-  id: null,
-  label: "",
-  bankName: "",
-  accountName: "",
-  accountNo: "",
-  branch: "",
-  ifsc: "",
-  isDefault: false,
-});
-
 export default function AppSettings({
   settings,
   onSaved,
@@ -68,7 +58,9 @@ export default function AppSettings({
   const [form, setForm] = useState<Settings>({ ...settings });
   const [diagnosticsOpen, setDiagnosticsOpen] = useState(false);
   const [banks, setBanks] = useState<BankAccount[]>([]);
+  const [bankModalOpen, setBankModalOpen] = useState(false);
   const [editing, setEditing] = useState<BankAccount | null>(null);
+  const bankLauncher = useRef<HTMLElement | null>(null);
   const [busy, setBusy] = useState(false);
   const toast = useToast();
   // One form state for every tab and one Save button, so edits survive switching tabs.
@@ -94,9 +86,6 @@ export default function AppSettings({
   const set = <K extends keyof Settings>(key: K, value: Settings[K]) =>
     setForm((prev) => ({ ...prev, [key]: value }));
 
-  const setBank = <K extends keyof BankAccount>(key: K, value: BankAccount[K]) =>
-    setEditing((prev) => (prev ? { ...prev, [key]: value } : prev));
-
   const registered = form.gstRegistration !== "unregistered";
   const gstinProblem = vendorGstinError(
     form.gstRegistration,
@@ -123,22 +112,19 @@ export default function AppSettings({
     }
   };
 
-  const saveBank = async () => {
-    if (!editing) return;
-    setBusy(true);
-    try {
-      const saved = await api.saveBank(editing);
-      if (saved.isDefault || form.defaultBankId === null) {
-        setForm((prev) => ({ ...prev, defaultBankId: saved.id }));
-      }
-      setEditing(null);
-      await loadBanks();
-      toast.success("Bank account saved", "Click Save settings to keep a changed default account.");
-    } catch (e) {
-      toast.error("Could not save bank account", String(e));
-    } finally {
-      setBusy(false);
+  const openBankEditor = (bank: BankAccount | null, trigger: HTMLElement) => {
+    bankLauncher.current = trigger;
+    setEditing(bank);
+    setBankModalOpen(true);
+  };
+
+  const onBankSaved = (saved: BankAccount) => {
+    if (saved.isDefault || form.defaultBankId === null) {
+      setForm((prev) => ({ ...prev, defaultBankId: saved.id }));
     }
+    setBankModalOpen(false);
+    void loadBanks();
+    toast.info("Click Save settings to keep a changed default account.");
   };
 
   const removeBank = async (bank: BankAccount) => {
@@ -306,12 +292,7 @@ export default function AppSettings({
             </TabPanel>
             <TabPanel>
       <section className="voiced-stack" style={{ marginBottom: "2rem" }}>
-        <div style={{ display: "flex", justifyContent: "space-between", alignItems: "center" }}>
-          <h3>Bank accounts</h3>
-          <Button kind="tertiary" size="sm" renderIcon={Add} onClick={() => setEditing(blankBank())}>
-            Add account
-          </Button>
-        </div>
+        <h3>Bank accounts</h3>
 
         {banks.length > 0 ? (
           <TableContainer>
@@ -336,7 +317,7 @@ export default function AppSettings({
                     <TableCell>{bank.isDefault ? "Yes" : "No"}</TableCell>
                     <TableCell>
                       <div className="voiced-header-action">
-                        <Button kind="ghost" size="sm" onClick={() => setEditing({ ...bank })}>
+                        <Button kind="ghost" size="sm" onClick={(e: MouseEvent<HTMLElement>) => openBankEditor({ ...bank }, e.currentTarget)}>
                           Edit
                         </Button>
                         <Button
@@ -358,78 +339,21 @@ export default function AppSettings({
           <div className="voiced-empty">No bank accounts yet.</div>
         )}
 
-        {editing ? (
-          <div style={{ border: "1px solid var(--cds-border-subtle-01)", padding: "1rem" }}>
-            <Grid narrow>
-              <Column sm={4} md={4} lg={6}>
-                <TextInput
-                  id="b-label"
-                  labelText="Label"
-                  value={editing.label}
-                  onChange={(e) => setBank("label", e.target.value)}
-                />
-              </Column>
-              <Column sm={4} md={4} lg={6}>
-                <TextInput
-                  id="b-bankName"
-                  labelText="Bank name"
-                  value={editing.bankName}
-                  onChange={(e) => setBank("bankName", e.target.value)}
-                />
-              </Column>
-              <Column sm={4} md={4} lg={6}>
-                <TextInput
-                  id="b-accountName"
-                  labelText="Account name"
-                  value={editing.accountName}
-                  onChange={(e) => setBank("accountName", e.target.value)}
-                />
-              </Column>
-              <Column sm={4} md={4} lg={6}>
-                <TextInput
-                  id="b-accountNo"
-                  labelText="Account number"
-                  value={editing.accountNo}
-                  onChange={(e) => setBank("accountNo", e.target.value)}
-                />
-              </Column>
-              <Column sm={4} md={4} lg={6}>
-                <TextInput
-                  id="b-branch"
-                  labelText="Branch"
-                  value={editing.branch}
-                  onChange={(e) => setBank("branch", e.target.value)}
-                />
-              </Column>
-              <Column sm={4} md={4} lg={6}>
-                <TextInput
-                  id="b-ifsc"
-                  labelText="IFSC"
-                  value={editing.ifsc}
-                  onChange={(e) => setBank("ifsc", e.target.value.toUpperCase())}
-                  invalid={Boolean(ifscError(editing.ifsc))}
-                  invalidText={ifscError(editing.ifsc)}
-                />
-              </Column>
-              <Column sm={4} md={8} lg={16}>
-                <Toggle
-                  id="b-default"
-                  labelText="Use as default account"
-                  toggled={editing.isDefault}
-                  onToggle={(value) => setBank("isDefault", value)}
-                />
-              </Column>
-            </Grid>
-            <div className="voiced-header-action" style={{ marginTop: "1rem" }}>
-              <Button size="sm" onClick={saveBank} disabled={busy}>
-                {busy ? "Saving…" : "Save account"}
-              </Button>
-              <Button kind="ghost" size="sm" onClick={() => setEditing(null)}>
-                Cancel
-              </Button>
-            </div>
-          </div>
-        ) : null}
+        <Button
+          kind="ghost"
+          size="sm"
+          renderIcon={Add}
+          onClick={(e: MouseEvent<HTMLElement>) => openBankEditor(null, e.currentTarget)}
+        >
+          Add bank account
+        </Button>
+        <BankAccountModal
+          open={bankModalOpen}
+          bank={editing}
+          launcherRef={bankLauncher}
+          onClose={() => setBankModalOpen(false)}
+          onSaved={onBankSaved}
+        />
       </section>
             </TabPanel>
             <TabPanel>
diff --git a/src/views/NewInvoice.tsx b/src/views/NewInvoice.tsx
index 7bb7519..b1e4dcf 100644
--- a/src/views/NewInvoice.tsx
+++ b/src/views/NewInvoice.tsx
@@ -72,6 +72,7 @@ import { withUserFonts } from "../lib/fontImport";
 import { ImagePicker } from "../components/ImagePicker";
 import { loadLogoImages, type LogoImages } from "../lib/logo";
 import ClientModal from "../components/ClientModal";
+import BankAccountModal from "../components/BankAccountModal";
 import { useToast } from "../components/ToastProvider";
 import { itemFromPreset } from "../lib/presets";
 
@@ -88,6 +89,9 @@ interface NewInvoiceProps {
   /** A draft to open as soon as the form is shown (set by "Duplicate" on the invoice page). */
   openDraftId?: number | null;
   onDraftOpened?: () => void;
+  /** Current theme ("g10" | "g100") and its single toggle handler, owned by App. */
+  theme?: string;
+  onToggleTheme?: () => void;
 }
 
 const AUTOSAVE_MS = 1000;
@@ -98,7 +102,7 @@ const formatStamp = (iso: string) => {
   return Number.isNaN(d.getTime()) ? iso : `${d.toLocaleDateString("en-GB")} ${formatTime(d)}`;
 };
 
-export default function NewInvoice({ settings, onSettingsChange, active, onActivate, openDraftId = null, onDraftOpened }: NewInvoiceProps) {
+export default function NewInvoice({ settings, onSettingsChange, active, onActivate, openDraftId = null, onDraftOpened, theme, onToggleTheme }: NewInvoiceProps) {
   const toast = useToast();
   const newItem = (): InvoiceItem => ({ ...EMPTY_ITEM, hsnSac: settings.defaultHsnSac });
   const blankState = (): InvoiceFormState => {
@@ -131,6 +135,8 @@ export default function NewInvoice({ settings, onSettingsChange, active, onActiv
   const [presets, setPresets] = useState<ItemPreset[]>([]);
   const [clientModalOpen, setClientModalOpen] = useState(false);
   const newClientButton = useRef<HTMLButtonElement | null>(null);
+  const [bankModalOpen, setBankModalOpen] = useState(false);
+  const newBankButton = useRef<HTMLButtonElement | null>(null);
   const [clientId, setClientId] = useState<number | null>(null);
   const [clientName, setClientName] = useState("");
   const [clientAddress, setClientAddress] = useState("");
@@ -678,6 +684,18 @@ export default function NewInvoice({ settings, onSettingsChange, active, onActiv
   // Yield the shared render worker to the export; the model changes back when it is done and re-renders.
   const pdf = useInvoicePdf({ model: busy ? null : previewModel, prefs: activePrefs });
 
+  const themeToggle = onToggleTheme ? (
+    <Toggle
+      id="themeToggle"
+      size="sm"
+      labelText="Dark mode"
+      labelA="Off"
+      labelB="On"
+      toggled={theme === "g100"}
+      onToggle={() => onToggleTheme()}
+    />
+  ) : null;
+
   return (
     <>
     <div className="voiced-page" hidden={!active}>
@@ -696,8 +714,9 @@ export default function NewInvoice({ settings, onSettingsChange, active, onActiv
                 )}
               </p>
             </div>
-            {locked ? null : (
+            {locked ? themeToggle : (
               <div className="voiced-header-action" style={{ flexWrap: "wrap" }}>
+                {themeToggle}
                 {draftSaving ? (
                   <InlineLoading status="active" description="Saving draft…" />
                 ) : savedAt && !unsaved ? (
@@ -1094,6 +1113,16 @@ export default function NewInvoice({ settings, onSettingsChange, active, onActiv
               />
             ))}
           </Select>
+          <Button
+            ref={newBankButton}
+            kind="ghost"
+            size="sm"
+            renderIcon={Add}
+            disabled={locked}
+            onClick={() => setBankModalOpen(true)}
+          >
+            Create bank account
+          </Button>
 
           <ImagePicker
             kind="signature"
@@ -1206,6 +1235,17 @@ export default function NewInvoice({ settings, onSettingsChange, active, onActiv
         </TableBody>
       </Table>
     </Modal>
+      <BankAccountModal
+        open={bankModalOpen}
+        bank={null}
+        launcherRef={newBankButton}
+        onClose={() => setBankModalOpen(false)}
+        onSaved={(saved) => {
+          setBankModalOpen(false);
+          setBankId(saved.id);
+          api.listBanks().then(setBanks).catch(() => {});
+        }}
+      />
       <ClientModal
         open={clientModalOpen}
         client={null}