diff --git a/src/__tests__/bank-accounts.test.ts b/src/__tests__/bank-accounts.test.ts
new file mode 100644
index 0000000..2045b6a
--- /dev/null
+++ b/src/__tests__/bank-accounts.test.ts
@@ -0,0 +1,152 @@
+import { describe, it, expect, beforeAll, afterAll } from "vitest";
+import Fastify from "fastify";
+import jwt from "jsonwebtoken";
+import bankAccountsRoutes from "../routes/admin/bank-accounts";
+import prisma from "../config/database";
+import { config } from "../config/env";
+
+// Fixture marker so cleanup never touches real data.
+const N = "bank_accounts_test_";
+
+let app: ReturnType<typeof Fastify>;
+let token: string;
+const createdIds: number[] = [];
+
+beforeAll(async () => {
+  app = Fastify({ logger: false });
+  await app.register(bankAccountsRoutes, {
+    prefix: "/api/admin/bank-accounts",
+  });
+
+  await prisma.users
+    .deleteMany({ where: { username: { startsWith: N } } })
+    .catch(() => {});
+
+  // Admin role bypasses the settings.banking permission guard.
+  const adminRole = await prisma.roles.findFirst({ where: { name: "admin" } });
+  if (!adminRole)
+    throw new Error("Test setup: no admin role found — seed the database");
+
+  const user = await prisma.users.create({
+    data: {
+      username: `${N}user`,
+      email: `${N}user@test.local`,
+      password_hash: "x",
+      first_name: "Bank",
+      last_name: "Test",
+      is_active: true,
+      totp_enabled: false,
+      role_id: adminRole.id,
+    },
+  });
+  token = jwt.sign(
+    { sub: user.id, username: user.username, role: "admin" },
+    config.jwt.secret,
+    { expiresIn: config.jwt.accessTokenExpiry },
+  );
+});
+
+afterAll(async () => {
+  if (createdIds.length) {
+    await prisma.bank_accounts
+      .deleteMany({ where: { id: { in: createdIds } } })
+      .catch(() => {});
+  }
+  await prisma.users
+    .deleteMany({ where: { username: { startsWith: N } } })
+    .catch(() => {});
+  await app.close();
+});
+
+const auth = { authorization: () => `Bearer ${token}` };
+
+describe("bank accounts — flat-body create/update persists all fields", () => {
+  it("creates an account from a flat top-level body and persists every field", async () => {
+    const payload = {
+      account_name: `${N}Hlavní účet`,
+      bank_name: "Komerční banka",
+      account_number: "123456789/0100",
+      iban: "CZ6508000000192000145399",
+      bic: "KOMBCZPP",
+      currency: "CZK",
+      is_default: true,
+    };
+
+    const post = await app.inject({
+      method: "POST",
+      url: "/api/admin/bank-accounts/",
+      headers: { authorization: auth.authorization() },
+      payload,
+    });
+    expect(post.statusCode).toBe(201);
+    const id = post.json().data.id as number;
+    expect(typeof id).toBe("number");
+    createdIds.push(id);
+
+    // Read back via the list endpoint and confirm NONE of the fields are blank.
+    const row = await prisma.bank_accounts.findUnique({ where: { id } });
+    expect(row?.account_name).toBe(payload.account_name);
+    expect(row?.bank_name).toBe(payload.bank_name);
+    expect(row?.account_number).toBe(payload.account_number);
+    expect(row?.iban).toBe(payload.iban);
+    expect(row?.bic).toBe(payload.bic);
+    expect(row?.currency).toBe("CZK");
+    expect(row?.is_default).toBe(true);
+  });
+
+  it("updates an account from a flat body that also carries the id", async () => {
+    const created = await prisma.bank_accounts.create({
+      data: { account_name: `${N}orig`, bank_name: "Orig", currency: "CZK" },
+    });
+    createdIds.push(created.id);
+
+    // Mirrors the client payload: spread fields + id (id routes the URL/method,
+    // is declared in the schema, and is ignored by the route which uses :id).
+    const put = await app.inject({
+      method: "PUT",
+      url: `/api/admin/bank-accounts/${created.id}`,
+      headers: { authorization: auth.authorization() },
+      payload: {
+        id: created.id,
+        account_name: `${N}upraveno`,
+        bank_name: "Nová banka",
+        iban: "CZ9999",
+        currency: "EUR",
+        is_default: false,
+      },
+    });
+    expect(put.statusCode).toBe(200);
+
+    const row = await prisma.bank_accounts.findUnique({
+      where: { id: created.id },
+    });
+    expect(row?.account_name).toBe(`${N}upraveno`);
+    expect(row?.bank_name).toBe("Nová banka");
+    expect(row?.iban).toBe("CZ9999");
+    expect(row?.currency).toBe("EUR");
+  });
+
+  it("rejects the old nested {bank:{...}} body shape with 400 (no silent blank save)", async () => {
+    const post = await app.inject({
+      method: "POST",
+      url: "/api/admin/bank-accounts/",
+      headers: { authorization: auth.authorization() },
+      payload: { bank: { account_name: `${N}nested`, bank_name: "X" } },
+    });
+    expect(post.statusCode).toBe(400);
+
+    // And nothing was persisted under that name.
+    const leaked = await prisma.bank_accounts.findFirst({
+      where: { account_name: `${N}nested` },
+    });
+    expect(leaked).toBeNull();
+  });
+
+  it("requires authentication", async () => {
+    const res = await app.inject({
+      method: "GET",
+      url: "/api/admin/bank-accounts/",
+    });
+    expect(res.statusCode).toBe(401);
+  });
+});
diff --git a/src/admin/pages/CompanySettings.tsx b/src/admin/pages/CompanySettings.tsx
index 0433bd6..2757abb 100644
--- a/src/admin/pages/CompanySettings.tsx
+++ b/src/admin/pages/CompanySettings.tsx
@@ -241,7 +241,7 @@ export default function CompanySettings({
   });
 
   const bankMutation = useApiMutation<
-    { id?: number; bank: BankForm },
+    BankForm & { id?: number },
     { message?: string }
   >({
     url: (input) =>
@@ -432,8 +432,8 @@ export default function CompanySettings({
     setBankSaving(true);
     try {
       const result = await bankMutation.mutateAsync({
+        ...bankForm,
         id: editingBank ?? undefined,
-        bank: bankForm,
       });
       alert.success(result?.message || "Uloženo");
       resetBankForm();
diff --git a/src/schemas/bank-accounts.schema.ts b/src/schemas/bank-accounts.schema.ts
index 9942c9d..b44dd7c 100644
--- a/src/schemas/bank-accounts.schema.ts
+++ b/src/schemas/bank-accounts.schema.ts
@@ -1,7 +1,13 @@
 import { z } from "zod";
 import { booleanFromForm, numberFromForm } from "./common";
 
-export const CreateBankAccountSchema = z.object({
+// `id` is declared (optional, ignored by the routes — they use the URL param)
+// only so the client may send it in the body for URL/method routing without a
+// strictObject rejection. strictObject is deliberate: a malformed/nested body
+// (e.g. the old `{ id, bank: {...} }` shape) now 400s loudly instead of
+// silently stripping every field and saving a blank record.
+export const CreateBankAccountSchema = z.strictObject({
+  id: z.number().int().optional(),
   account_name: z.string().max(255).nullish(),
   bank_name: z.string().max(255).nullish(),
   account_number: z.string().max(255).nullish(),
@@ -12,7 +18,8 @@ export const CreateBankAccountSchema = z.object({
   position: numberFromForm.optional().default(0),
 });
 
-export const UpdateBankAccountSchema = z.object({
+export const UpdateBankAccountSchema = z.strictObject({
+  id: z.number().int().optional(),
   account_name: z.string().max(255).nullish(),
   bank_name: z.string().max(255).nullish(),
   account_number: z.string().max(255).nullish(),