I'm stumped and a call to the tax man was unfruitful so here goes.

I've recently received back pay to the tune of 20k dating back to 2004. If I'd received the correct money since 2004 I would have been paying the normal tax rate, but having it in a lump sum in 2009 almost the full back pay has been slapped with 40% tax.

Has anyone had a similar experience and has any sort of advice? I'm figuring at's a few K's difference that I'm squabbling about which is at least a Carbon Blur frame for free.

Any help appreciated.

I think it'll depend whether the back pay was the result of a mistake – in which case your employer will have to sort it out for each year and reopen each year's tax account
If it was a recent agreement – the tax will be due when it's paid

No mistake; I was awarded/negotiated the pay rise in 2004 it only took until now to pay up. Essentially I have been underpaid since 2004.

So it was a mistake? – they forgot to pay you

AFAIK – my first option should apply

Discuss with your union/professional body where you stand on this, and whether the Trust has some obligation to make the problem right, or will it mean your tax code alters in the next financial year to compensate?