your eTax sign-in is deleted straight away, and the app stops working for you
you will not be able to sign in again with this email address
your bookkeeping records, receipts and anything already filed with HMRC are kept — the law requires us to keep them (five years under the money-laundering rules, and longer where the tax rules say so), so we cannot delete them
your accountant is told, so nothing is left half-finished
This cannot be undone from the app. If you wanted to come back afterwards, you would need to speak to your accountant.