I need to "update my tax affairs" and no idea how

TW25

Hopefully someone can point me in the right direction.....

I lived overseas for 5 years and was doing self-assessment UK tax returns whilst there.  On the year I moved back (July 2015) my company did USA tax returns for me.  In March 2016 my company paid me a small bonus in USA for 2015 work year, and in April 2016 I cashed in my 401k (pension) - which I paid USA tax and a fine for early withdrawl due to age.  The company did complete the USA tax return for 2016 as well.  My company also took care of UK tax return to the year ending April 2016.  After that I didnt do a tax return anymore and just returned to PAYE.  Going back to the USA money, in June of 2016 I moved most of the $ to my UK bank account.

Recently, I have been sent a letter from Tax authorities in UK, saying they have been alerted to undeclared offshore income or gain.  But the helpline didnt give me any details at all about what it was.  I have been instructed to update my tax affairs, and in the meantime moved to an emergency tax code (basically no personal allowance).

Seeking some help/guidance on where to start with this, as I really have no clue.  is this something I can do/find online, or (as I suspect) I need to find someone to help me.  If its the latter, any recommendation or suggestions what kind of person I need to find to help me clean this up, and I hope claim back the overpaid tax for last tax year - or pay what I owe on overseas income..... although I believed I was paying what was due in USA (as I had done when I lived there without issues).

Thank you in advance.

xylophone

You indicate that a UK tax return was submitted for the year 2015-16.

As a start, you might print off tax returns for 16/17, 17/18, 18/19/,19/20 and complete them  - this should give you some indication as to the state of your affairs?

If you find yourself out of your depth, a tax accountant (Chartered Tax Advisor)  should be able to assist.