Multinational Top-up Tax and Domestic Top-up Tax

MTT53010 - Administration: The self-assessment return: Overview

The filing member of a registered group (see MTT51400) must submit a self-assessment return to HMRC for each accounting period, unless it has submitted a below-threshold notification.

The submission of the return will form the self-assessment of the group’s total MTT liability as well as the liability of each member of the group for the period.

A self-assessment return or below-threshold notification must be submitted by all registered groups, including groups that do not have any MTT liability for the period and groups that do not have any responsible members in the UK for the period.

See MTT53200 for guidance on below-threshold notifications.

This is set out in part 5, schedule 14 to Finance (No.2) Act 2023.

Filing date

A self-assessment return, or valid below-threshold notification, must be submitted to HMRC within 15 months of the end of the accounting period.

However, a group has 18 months to submit the self-assessment return for the first accounting period it is subject to MTT.

The filing date for a return cannot fall before 30 June 2026. Where the deadline would fall before this date, the filing date will instead be 30 June 2026.

See MTT55440 for guidance on penalties relating to the self-assessment return.

Amendments

The filing member may amend a self-assessment return by submitting a notice to HMRC. A return may be amended any number of times.

The time limit is 12 months beginning with the filing date (regardless of when the return was actually submitted).

HMRC will issue a notice to specify how amendments must be submitted.