Thanks for the advice. I phoned them this morning and asked to make a Voluntary Disclosure. They told me they would send me a form with a voluntary discoloure number that i would need to fill in. I would then be able to use this number to complete my returns online within 60 days and use an online calculator that will calculate exactly what i owe. They also said that i would need to select the level of penalty, and recommended that most people in my position go for 10% - which seems more than fair to me. Thanks so much for the advice, so glad i got this in the open. It looks like it wont be as bad as i thought and i can just pay the tax and the penalty, move on and learn from my mistakes. cheers

Please help i have made a big mistake and not filed any self assessment tax forms for secondary income i have received in the past 3 years. I am employed already and built a few websites on the side not fully realising the imapact of not declaring the income. I think i owe between £1600-£2000, and i expect i will also have to pay penalties. I want to pay, but am worried that my employer will find out and what hmrc will say. I realise my mistake now and want to end this - please help.