UK Messed up my self assessment

[Scared]

I have just realised that I have messed up my last 2 self assessment tax returns. In a nutshell, I am a landlord and have claimed the capital element of my mortgage as well as the interest as an allowable expense. Can someone please advise how best to inform HMRC and what penalties I could face?

I recalculated what my payment should have been and it looks like I have underpaid by £450 for the 2 years. I am especially concerned as I am a newly qualified management accountant and am worried what the consequences could be on my career. Could I receive a criminal record or lose my membership? Are HMRC likely to delve deeper into the matter given that I am an accountant, albeit not a tax specialist? I really hope not as this was an honest mistake and from what I have read plenty of accountants make greater mistakes on their clients tax returns.

Any light anyone can shed would be very much appreciated

Many thanks

 

[weaves77]

File an amended return. You can probably do this with no questions asked as you are saying you Iowe more. If you file on line via an accountancy system you cancerainly send this years on there.
If sending an amended paper return advise that this is a mistake and the wrong figures were taken by mistake and you are disclosing this info. Should be fine don't panick