As the HMRC service was not used to file a tax return for this year, you can't use the service

Hi I went into today to amend a self assesment (that was submitted about 10 days ago). Now I get this message As the HMRC service was not used to file a tax return for this year, you can't use the service to amend that return Even though a) I did use HMRC service (i.e. the website) and b) I've never used any other methods Any way to remedy this other than call up and be on hold for a long time? thanks!

Hi,

If you are having issues accessing your online account to amend a submitted tax return then please contact our online services team for assistance.

Technical support with HMRC online services

Thank you.