*Disclaimer:
Whilst the Marriage Allowance Transfer (MAT) can be claimed as a domiciled non-resident who's resided in the UK previously, HMRC do NOT provide for the automatic adjustment of MAT on a non-resident status tax return. The transfer has to be claimed seperately here.
To enter the Marriage Allowance Transfer claim you will first need to amend your Personal Details to include your Spouse/Civil Partner details. Ensure you click 'Yes' to the box stating 'DO YOU INTEND TO CLAIM MARRIAGE (TRANSFER) ALLOWANCE OR MARRIED COUPLES ALLOWANCE (DOB PRE 06/04/1935)? IF SO PLEASE CHOOSE YES BELOW?'
This is where you'd fill in your spouses personal details.
You will also have to answer to some questions on the almost there page. You will sent to the 'Almost there' page when you go through the 'validate my tax return' process.
The response to the question results in HMRC adjusting the filed self-assessment return to reflect the transfer claim.
No change in the calculation of tax on your return is visible other than the response itself. When you return has been received by HMRC they will then validate the claim and adjust your tax calculation accordingly.
Please note: You must first make a claim via the HMRC website at https://www.gov.uk/apply-marriage-allowance