Your situation is not unusual and the Tax Aid web site has some very
useful advice which will answer your question.
Tax Aid is charity which gives advice on tax issues. Their home page is,
The page you require is,
?If you have not declared your income?
I recommend that you read the page as it is very detailed, but this is
a sample of their good advice.
?While we would advise you to report your failure to HM Revenue and
Customs as soon as possible, it is usually a good idea to seek advice
from an accountant or tax adviser first. After reviewing the
situation, they may be able tell you how much tax you have failed to
pay, how seriously HM Revenue and Customs will view your situation,
and how best to approach HM Revenue and Customs.
HM Revenue and Customs has established a confidential helpline
(0845 608 6000) which you may contact to discuss your situation,
without revealing your identity.
This may be a good way of initiating contact with HM Revenue and Customs.
Once you have clarification from the helpline as to how HM Revenue and
Customs will view your situation, you may decide to give them your
identity and they will pass your case to a tax office to continue
negotiations with you.?
If you contact Tax Aid, the charity will also give advice from their experts.
As the article above indicates, a good accountant will also assist you
or you could also seek advice from the Citizens Advice Bureau.
This is the web page for the HM Customs and Excise, Tax and Benefits
I hope this answers your question. If it does not, or the answer is
unclear, then please ask for clarification of this research before
rating the answer. I shall respond to the clarification request as
soon as I receive it.
A link from a BBC article on failing to pay tax