Whereas in the UK a number of benefits have application/renewal forms that look a lot like a tax return but are actually separate.
Not all higher rate tax payers have to do a return either. (Then again with gift aid and pension contributions relief even defining a higher rate tax payer can get complex - there was a big fuss recently over child benefit and the fact a particular claw back only applied to net relevant earnings rather than all earnings)
And often you can simply write a letter, in simple cases you don't have to file a full return.
I was thinking about suggesting the same thing - and also wondering what the rules in countries are.
The register say it has not done yet http://www.theregister.co.uk/2010/04/08/mandybill_last_day/