Need a letter for mortgage lender for self assesment tax return

Accountant needed to optimise your tax returns to improve affordability with HSBC lender.

I have a company and all the accounts with that are fine.

I have received additional income this year from p/t consultancy work but I have not registered with HMRC as sole trader.

I have submitted provisional figures for self assessment 24-25 and need to edit them to reflect the "other income" that I have. Need advice on this so that it is accepted my mortgage lender. Will need a letter from you as my accountant. I don't have one for my self assessment, only for the business when I need it for mortgage purposes - I am a first time buyer.