diff --git a/routes/wallet.ts b/routes/wallet.ts
index 15629bb437d..5561c7cd43d 100644
--- a/routes/wallet.ts
+++ b/routes/wallet.ts
@@ -7,6 +7,24 @@ import { type Request, type Response, type NextFunction } from 'express'
 import { WalletModel } from '../models/wallet'
 import { CardModel } from '../models/card'
 
+const MIN_TOP_UP_AMOUNT = 10
+const MAX_TOP_UP_AMOUNT = 1000
+
+function parseTopUpAmount (value: unknown): number | null {
+  const amount = typeof value === 'number' ? value : (typeof value === 'string' && value.trim() !== '' ? Number(value) : NaN)
+  if (!Number.isInteger(amount) || amount < MIN_TOP_UP_AMOUNT || amount > MAX_TOP_UP_AMOUNT) {
+    return null
+  }
+  return amount
+}
+
+function isCardExpired (card: CardModel): boolean {
+  const now = new Date()
+  const year = now.getFullYear()
+  const month = now.getMonth() + 1
+  return card.expYear < year || (card.expYear === year && card.expMonth < month)
+}
+
 export function getWalletBalance () {
   return async (req: Request, res: Response, next: NextFunction) => {
     const wallet = await WalletModel.findOne({ where: { UserId: req.body.UserId } })
@@ -20,12 +38,17 @@ export function getWalletBalance () {
 
 export function addWalletBalance () {
   return async (req: Request, res: Response, next: NextFunction) => {
-    const cardId = req.body.paymentId
-    const card = cardId ? await CardModel.findOne({ where: { id: cardId, UserId: req.body.UserId } }) : null
-    if (card != null) {
+    const amount = parseTopUpAmount(req.body.balance)
+    if (amount === null) {
+      res.status(400).json({ status: 'error', message: `Top-up amount must be a whole number between ${MIN_TOP_UP_AMOUNT} and ${MAX_TOP_UP_AMOUNT}.` })
+      return
+    }
+    const cardId = Number(req.body.paymentId)
+    const card = Number.isInteger(cardId) && cardId > 0 ? await CardModel.findOne({ where: { id: cardId, UserId: req.body.UserId } }) : null
+    if (card != null && !isCardExpired(card)) {
       try {
-        await WalletModel.increment({ balance: req.body.balance }, { where: { UserId: req.body.UserId } })
-        res.status(200).json({ status: 'success', data: req.body.balance })
+        await WalletModel.increment({ balance: amount }, { where: { UserId: req.body.UserId } })
+        res.status(200).json({ status: 'success', data: amount })
       } catch {
         res.status(404).json({ status: 'error' })
       }
diff --git a/test/api/wallet.test.ts b/test/api/wallet.test.ts
index a3ff16d452a..e576e2a9dca 100644
--- a/test/api/wallet.test.ts
+++ b/test/api/wallet.test.ts
@@ -58,6 +58,43 @@ void describe('/api/Wallets', () => {
     assert.equal(balanceRes.body.data, 210)
   })
 
+  void it('PUT charge wallet with negative amount is rejected', async () => {
+    const res = await request(app)
+      .put('/rest/wallet/balance')
+      .set(authHeader)
+      .send({ balance: -500, paymentId: 2 })
+    assert.equal(res.status, 400)
+  })
+
+  void it('PUT charge wallet with amount above maximum is rejected', async () => {
+    const res = await request(app)
+      .put('/rest/wallet/balance')
+      .set(authHeader)
+      .send({ balance: 999999, paymentId: 2 })
+    assert.equal(res.status, 400)
+
+    const balanceRes = await request(app)
+      .get('/rest/wallet/balance')
+      .set(authHeader)
+    assert.equal(balanceRes.body.data, 210)
+  })
+
+  void it('PUT charge wallet with non-numeric amount is rejected', async () => {
+    const res = await request(app)
+      .put('/rest/wallet/balance')
+      .set(authHeader)
+      .send({ balance: 'lots', paymentId: 2 })
+    assert.equal(res.status, 400)
+  })
+
+  void it('PUT charge wallet with non-integer amount is rejected', async () => {
+    const res = await request(app)
+      .put('/rest/wallet/balance')
+      .set(authHeader)
+      .send({ balance: 10.5, paymentId: 2 })
+    assert.equal(res.status, 400)
+  })
+
   void it('PUT charge wallet from foreign credit card is forbidden', async () => {
     const res = await request(app)
       .put('/rest/wallet/balance')