Tax codes in Vietnam: enterprise codes, branch codes and the switch to personal identification numbers

In Vietnam, the tax code (mã số thuế, often shortened to MST) is the key that links a taxpayer to every return, payment and invoice in the tax system. For a company, the enterprise code issued at business registration is also its tax code, so there is no separate tax registration step for the head office. Branches and other dependent units receive codes derived from the parent's. For individuals, the picture changed on 1 July 2025: the personal identification number now replaces the personal tax code.

These codes are the plumbing of the system. When they are wrong — a supplier invoice issued to a branch code instead of the head office, a Vietnamese employee still recorded under an old personal tax code, an expatriate without any registration — the consequences show up far from the original mistake: rejected expense deductions, PIT finalisation errors, or an invoice that does not match on the tax authority's side. This guide explains how the codes are structured and what to keep in order.

Company codes: one number from registration onwards

When a company is registered, the business registration authority issues an enterprise code that the tax system uses as the company's tax code. It is a 10-digit number, and it stays the same for the life of the company even when the name, address, capital or legal representative changes. Your e-invoices, returns, bank payment references and contracts should all carry the same code.

For foreign-invested enterprises, two points often cause confusion:

• The investment registration certificate has its own project number. It is not a tax code. Incentives attach to the project, but returns are filed under the enterprise's tax code.
• A representative office is not a company. A foreign company's representative office has a tax code for withholding PIT on its staff, but it cannot trade or issue sales invoices.

Branches and dependent units

A branch, a business location or another dependent unit receives a 13-digit code: the parent's 10 digits followed by a three-digit suffix. Whether the unit files its own returns depends on how it is organised and which taxes arise there. A branch in another province that sells goods and issues invoices will typically have its own VAT obligations; a warehouse that only stores goods may not file anything separately.

What matters in daily work:

• Invoices must carry the right code. If a supplier invoices your branch but the cost belongs to the head office — or the reverse — the input VAT and the expense may end up in the wrong entity's books. Tell suppliers which code to use for which contract.
• Closing a branch is a tax procedure too. Its code must be terminated through the tax authority after its obligations are settled. Branches closed on the business registration side but left open on the tax side are a regular source of unexpected notices.
• The root is shared. Because the first 10 digits identify the parent, a lookup by the root code shows all dependent units. Use that to check that your list of branches matches the tax authority's list.

Individuals: personal identification numbers since July 2025

From 1 July 2025, a Vietnamese individual's personal identification number — the 12-digit number on the citizen identity card — is used in place of the personal tax code. For an employer, that means:

1. Update payroll master data so that each Vietnamese employee's record carries the identification number, and keep the former tax code in a separate field for historical reconciliation.
2. Use the identification number in PIT returns and withholding certificates for periods from the switch.
3. Check dependants. Dependants registered for family deduction are also identified by their identification numbers where they have one. Mismatches between names, dates of birth and numbers are the most common reason a dependant is not recognised.

Expatriates do not have a Vietnamese identification number. They still need a tax registration, which the employer normally handles when the expatriate starts work. Keep the resulting code in the payroll record and on the expatriate's file; it is needed for their annual PIT finalisation and, where relevant, for a tax residence certificate or treaty claim.

Family deductions are set at VND 15.5 million per month for the taxpayer and VND 6.2 million per month for each registered dependant from the 2026 tax year, under Resolution 110/2025/UBTVQH15. A dependant who is not properly registered is simply not counted, so the registration data has a direct effect on take-home pay.

Changing registration details

A company must keep its tax registration data current. Changes on the business registration side — name, address, business lines, legal representative, charter capital — flow to the tax authority through the shared registration system, but not every item flows automatically, and some changes need a separate tax filing. Examples that deserve a check:

• A change of managing tax office following an address move to another province.
• The accounting method, financial year or tax filing period (monthly or quarterly).
• Opening or closing bank accounts used for tax payments and refunds.
• Adding or closing branches and business locations.

The rules on tax registration were set for some years by Circular 86/2024/TT-BTC. From 1 July 2026, Circular 90/2026/TT-BTC on tax registration applies to procedures from that date. We name the documents so you know where to look; confirm the exact form and deadline in the text in force when you make the change.

Keeping codes clean in the ERP

Most code errors are data errors, and they are cheapest to fix in the master files rather than transaction by transaction. A short routine, run once a quarter, catches most of them:

1. Supplier master. Export the list of active suppliers with their tax codes and run them through the taxpayer lookup. Flag any code that no longer resolves, any name that no longer matches, and any status other than active.
2. Customer master. Do the same for customers you invoice. A buyer's code on your e-invoice that does not match the tax authority's record creates a problem for your buyer's input VAT, and a customer complaint for you.
3. Entity list. Compare your own list of branches and business locations with the dependent units shown under your 10-digit root. Close anything that should not be there.
4. Payroll. Check that every Vietnamese employee has an identification number on file and every expatriate has a registered tax code before the first payroll of a new year.

Keep the output of each run. When an auditor asks how you monitor counterparties, a dated file of quarterly checks is a better answer than a policy document.

What the status of a code tells you

The taxpayer lookup shows a status for each code. Two statuses come up often when checking suppliers and customers. Status 03 means the taxpayer has ceased operating but has not completed the procedure to terminate its tax code. Status 06 means the taxpayer is not operating at its registered address.

A status is information, not a verdict. It does not by itself tell you whether a company owes tax, whether its past invoices are valid, or whether it is acting in good faith. What it does tell you is that a transaction with that counterparty deserves a closer look — confirming the invoice on the e-invoice portal, checking the contract and payment trail, and asking questions before paying.

The context in 2026 makes this more relevant. Under dispatch 18/CĐ-CT of 13 July 2026, the tax authority opened a campaign to clean up tax code records. The review list as of July 2026 covered 617,462 enterprises: 291,962 that had stopped operating without completing dissolution, and 325,500 not operating at their registered address with tax debts. Some of those names may be in your supplier master file.

Our sister site TraThue.com (in Vietnamese) explains each status and the usual next step.

Where to check codes yourself

• The taxpayer information lookup — search by tax code to see status, name and managing office. Search by the 10-digit root to see dependent units.
• Your e-tax account — shows your registration data as the tax authority holds it. Compare it with your business registration certificate once a year.
• The e-invoice portal — confirms that invoices issued to you carry your correct code, and that invoices you issue reached the system.
• Your managing tax office — for corrections you cannot make online.