03 CASE OF DECLARING INVOICE ADJUSTMENTS UNDER CIRCULAR NO. 91/2026/TT-BTC

With the issuance of Circular No. 91/2026/TT-BTC, the regulations governing the declaration of adjusted invoices have been clarified, enabling businesses to determine the correct tax declaration period for each specific situation.

Below is a summary of the three most common cases that accountants should understand.

1. The Original Invoice Is Correct, but an Economic Event Occurs Later

This applies to cases where the original invoice was issued correctly, but subsequent economic events require an adjustment, such as:

• Commercial discounts;
• Returned goods;
• Cancellation or partial termination of a contract;
• Adjustments to services or real estate transactions for which payment was received in advance;
• Other similar post-invoice economic events.

These situations are not considered invoice errors, but rather economic events occurring after the invoice issuance.

Tax Declaration

• Seller: Declares the adjustment in the tax period in which the adjustment invoice is issued.
• Buyer: Declares the adjustment in the tax period in which the adjustment invoice is received.

Legal basis: Clause 5 and Point (d), Clause 6, Article 10 of Circular No. 91/2026/TT-BTC.

2. Errors in Output Invoices

Where an output invoice contains errors (e.g., incorrect revenue, VAT rate, VAT amount, product description, quantity, or unit price), the seller must issue either an adjustment invoice or a replacement invoice in accordance with the regulations.

Important Note

For all cases involving errors in output invoices, once an adjustment or replacement invoice is issued, the seller is required to submit a supplementary tax declaration for the original tax period in which the incorrect invoice was declared. These adjustments cannot be declared in the current tax period.

3. Errors in Input Invoices

For input invoices, the declaration method depends on the tax impact of the error.

Supplementary Declaration for the Original Tax Period Is Required If:

• The error increases the tax payable; or
• The error reduces the amount of tax already refunded.

Declaration in the Current Tax Period Is Allowed If:

In all other cases that do not increase the tax payable or reduce the refunded tax, the taxpayer may declare the adjustment in the current tax period.

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