HMRC's message · HTTP 400
The specified tax year is not supported. The tax year specified is before the minimum tax year value
When it appears
Any income tax request that names a tax year.
What to check
- The tax year the software is working in for this client.
- Whether the work belongs on an ordinary Self Assessment return.
How to fix it
Move to a supported tax year. Earlier years go on a Self Assessment return.
Making Tax Digital in Accountin
Accountin shows HMRC's code and message next to a plain explanation, and keeps HMRC's reply against every submission.