Where might I find my "Unique Taxpayer reference" (UTR)?

[HauntedLittleLunatic]

I need to fill out a tax return as - according to calculations I owe the tax man approx £100

Went online a few weeks ago to find telephone number but there was none - but there was a link to register for self assessment online. Didn't do it at the time as I didn't have all the paperwork I needed to hand.

Just sat down to do it and in order to register it is asking for my unique tax payer reference. Where might I find this? Do I have to ring them for it. I was hoping I would be able to do this tonight so that I can renew my tax credits this week before the deadline....

I have to complete a tax return to (presumably) get a formal calculation of my income (cos it is from multiple sources - although I think I am capable of adding them up myself).

I need my total income to renew tax credits.

I have never had to file a tax return...and not sure what correspondance I would from them which doesn't relate to tax credits (and only has NI number on).

It's on the paperwork from HMRC. I always have to dig around to find it. Twice a year, every year, I manage to hide it somewhere so I can't find it next time. And then there's the ruddy password for self-assessment online. It's a wonder I ever manage to pay them any tax at all, tbh.

I'm not self employed. I have just been fortunate to recieve a taxable payment which has not been taxed correctly.

Thanks for the helpline. Will call on Monday.

I might have to go with the estimated amount...my plan was to use the tax credits renewal to force me to do the self assessment.