diff --git a/src/backend/stores/user/UserStore.test.ts b/src/backend/stores/user/UserStore.test.ts
index 1fc80e87b..5f37d2394 100644
--- a/src/backend/stores/user/UserStore.test.ts
+++ b/src/backend/stores/user/UserStore.test.ts
@@ -54,4 +54,38 @@ describe('UserStore', () => {
         expect(typeof cachedUser?.email_confirmed).toBe('boolean');
         expect(typeof cachedUser?.requires_email_confirmation).toBe('boolean');
     });
+
+    it('counts other accounts holding the same phone number', async () => {
+        const phone = `+1415555${Math.floor(1000 + Math.random() * 9000)}`;
+        const makeUser = async () => {
+            const username = `up-${Math.random().toString(36).slice(2, 10)}`;
+            const user = await server.stores.user.create({
+                username,
+                uuid: uuidv4(),
+                password: null,
+                email: `${username}@test.local`,
+            });
+            await server.stores.user.update(user.id, { phone });
+            return user;
+        };
+
+        const first = await makeUser();
+        expect(
+            await server.stores.user.countOthersByPhone(phone, first.id),
+        ).toBe(0);
+
+        const second = await makeUser();
+        expect(
+            await server.stores.user.countOthersByPhone(phone, first.id),
+        ).toBe(1);
+        expect(
+            await server.stores.user.countOthersByPhone(phone, second.id),
+        ).toBe(1);
+        // A caller that isn't among the holders sees both.
+        expect(await server.stores.user.countOthersByPhone(phone, -1)).toBe(2);
+        // Unknown number counts zero.
+        expect(
+            await server.stores.user.countOthersByPhone('+19995550000', -1),
+        ).toBe(0);
+    });
 });
diff --git a/src/backend/stores/user/UserStore.ts b/src/backend/stores/user/UserStore.ts
index 535189996..efc283be7 100644
--- a/src/backend/stores/user/UserStore.ts
+++ b/src/backend/stores/user/UserStore.ts
@@ -257,6 +257,29 @@ export class UserStore extends PuterStore {
         return this.getById(row.id as number);
     }
 
+    /**
+     * Count accounts other than `excludeUserId` whose confirmed `phone`
+     * equals this number. Backs the cap on live accounts per phone number
+     * (the row is deleted with the account, so this only counts accounts
+     * that still exist — recycling velocity is rate-limited separately by
+     * the abuse policy's KV log).
+     *
+     * Not cached — like `getByCleanEmail`, callers use this for duplicate
+     * detection at write time, which needs fresh reads.
+     */
+    async countOthersByPhone(
+        phone: string,
+        excludeUserId: number,
+    ): Promise<number> {
+        if (!phone) return 0;
+        if (!isStorableAsLatin1(phone)) return 0;
+        const rows = (await this.clients.db.tryHardRead(
+            'SELECT COUNT(*) AS n FROM `user` WHERE `phone` = ? AND `id` != ?',
+            [phone, excludeUserId],
+        )) as Array<{ n: number | string }>;
+        return Number(rows[0]?.n) || 0;
+    }
+
     /**
      * Generic property lookup. Fast-path reads redis first (cache is
      * multi-key — every identifying property points at the same serialized
diff --git a/src/gui/src/UI/UIWindowPhoneVerificationRequired.js b/src/gui/src/UI/UIWindowPhoneVerificationRequired.js
index 59467d9f6..ee427d1f1 100644
--- a/src/gui/src/UI/UIWindowPhoneVerificationRequired.js
+++ b/src/gui/src/UI/UIWindowPhoneVerificationRequired.js
@@ -44,6 +44,8 @@ import {
 const SEND_REASON_MESSAGES = {
     phone_already_used:
         'This phone number has already been used to verify the maximum number of accounts. Please use a different number, or email support@puter.com for help.',
+    phone_verify_limit:
+        'This phone number cannot be used to verify this account. Please use a different number, or email support@puter.com for help.',
     phone_send_limit:
         'This phone number has received too many verification codes recently. Please try again later, or use a different number.',
     phone_verify_attempts_exhausted: