Sample instalment phone contract with a device lock clause

ABMDM Editorial Team. Published: 02/11/2026.

What should an instalment phone sale contract include?

An instalment phone contract should be in writing and state the device (model, serial/IMEI), the price, the payment schedule, and that the seller keeps title until the customer has paid in full. The basis is Article 453 of Vietnam's Civil Code 2015 on sales with deferred or staged payment; Article 331 requires a retention of title to be in a separate written document or stated in the sale contract itself. The buyer may use the phone while paying.

If the shop manages the phone with MDM, the contract should have its own section on that, so the customer knows in advance how the phone is managed. Article 331 also says retention of title takes effect against third parties from the time it is registered (source); ask a lawyer how registration works in practice. The ownership model in detail: iPhone instalments with MDM.

Sample device management and lock clause (for reference)

The text below is for reference only and does not replace a lawyer. Have the shop's lawyer review it before use. Blanks marked …… are for you to fill in with the customer. It is a translation of the Vietnamese template; give customers the Vietnamese version.

Article …. Device management during the instalment period

1. Party A (the shop) sells Party B (the customer) the device ……, serial/IMEI ……, on instalments. Party A keeps title to the device until Party B has paid the full amount under this contract.
2. Party B may use the device during the instalment period and shall take proper care of it.
3. Party B agrees that the device is enrolled in the mobile device management (MDM) system used by Party A, and shall not remove it from that system until the contract is paid off.
4. If a payment is due and Party B has not paid, Party A may remind Party B on the device and by text message to Party B's phone number, only between 7am and 9pm.
5. If payment is overdue, Party A may restrict the device in three tiers, counted from the days overdue: tier 1 after …… days (a reminder is shown and some entertainment apps are blocked); tier 2 after …… days (more apps restricted; calls can still be made and received); tier 3 after …… days (device locked, with only the payment screen and emergency calls). At every tier Party B can still reach Party A on ……, and has a way to pay on the screen.
6. When Party B pays the overdue amount in full, Party A lifts the restrictions as soon as possible and no later than ……. Unlocking may happen automatically when the transfer is received.
7. Party A views the device location only when an instalment is overdue or the device is reported lost, and every view is logged. Party A does not read Party B's messages, calls, photos, email, passwords or browsing history.
8. Party B agrees to Party A processing the data in clause 7 for this purpose. Party B may withdraw consent as the law allows; the consequences of withdrawal are agreed at ……
9. When Party B has paid in full, ownership passes to Party B and Party A removes the device from the management system within ……. Party B can check on the device that the management entry is gone.

Why each clause is written this way

• Clauses 1–2, Article 453: title is kept until paid in full and the buyer uses the phone meanwhile. It must be in writing (source).
• Clause 3: ABMDM blocks removal of management on a supervised device. The clause warns the customer in advance; how it works is under device financing.
• Clause 4: ABMDM sends reminders only from 7am to 9pm, and only to the person named on the contract.
• Clause 5: this is ABMDM's tiered lock; you set the days. Each tier is explained in tiered locks, and the setup is in set up lock tiers. Writing "not a dead end" into the contract also reassures the customer.
• Clause 6: the customer pays and the phone unlocks, automatically if you have connected VietQR.
• Clauses 7–8: location is sensitive data under the 2025 Personal Data Protection Law; see the 2025 law explained. Put it in its own clause so the customer sees what they agree to. Have a lawyer draft the withdrawal part.
• Clause 9: a paid-off phone must not stay in the shop's MDM.

What not to put in the contract

• A right to lock outside 7am–9pm, or to lock a relative's phone.
• A right to wipe the phone over a few late days. A wipe is a different command from a lock.
• A right to read the phone's content. ABMDM cannot read it, and you should not promise it.
• Penalties and late-payment interest: a lawyer should check these against current rules, so this article gives no figures.

Before you use the sample

Give the sample to the shop's lawyer, especially the parts on retention of title, registration and personal data (laws change; the Civil Code 2015 has been amended by Law 142/2025/QH15, per luatvietnam). Then test the exact days and reminder text on one shop device. For help setting tiers, call 0913 081 986 (8am–9pm).