Hi Samjam
Naughty boy! You wouldnt have had to pay tax anyway until about a year and six months after you had started, and even then only if you'd earned over the personal allowance limit (cant remember exactly, but its about £4500)
If you tell them you are starting now, they'll probably ask a few questons about how you have been affording to live. If you dont have good answers, you might be investigated. (ALL your financial affairs for the previous 6 years. They have the power to request your bank statements directly from your bank)
If you just tell the truth, the worst you'll get is a £100 penalty for late notification, and maybe a bill for the NI you mssed (£2 a week) They'll send you a tax return for the year ending april 5 2003, which will have to be in by January 31st 2004.
Personally, I recommend just coming clean. Apart from any moral question, they are much more likely to initiate a full investigation if you act dodgey, or tell them one thing then another.
Why didnt you tell them when you started? Avoiding tax is not a good idea. Tax pays for things we all use and need, fire service, police, hospitals, schools. When people avoid paying, it makes it more expensive for the rest of us.
Silly