intrest calculations on overpayments held on account

[keving]

hi having just come out of a 4 year tax investigation and having extra tax /penaltys & intrest to pay ,i am also due a rebate ,and as they have held my overpaid tax for some years , can anyone give me a rough idea of how much intrest i should be due on the sums below of prepaid tax as held by hmrc
06/07 £5700.89 overpaid
07/08 £5510.45 overpaid
08/09 £3100.89 overpaid
i know it wont be so much but as hmrc have charged me intrest on tax owed ,i can not see on the statement where i have been allocated my intrest due
i have not yet recieved my rebate but had a statement of the above
i will be greatfull for any help
regards

[mullet]

If they are using the overpayments against identified liabilities for other years, then they will not add repayment supplement (interest). What happens is that each year's overpayment has an "effective date of payment" which is the "balancing payment" date for each year:

2006-07 - 31-01-2008
2007-08 - 31-01-2009
2008-09 - 31-01-2010

It's easier to think of it in terms of a specific year. Say you owed £10,000 for 2004-05 and had overpaid £6,000 in 2006-07. Interest would run on £6,000 from 31-01-2006 to 31-01-2008 and from 31-01-2006 to the date of payment on the balance. So you do get the benefit from the "early" payment, but not through interest being added or paid to you. In effect the interest that you are charged is reduced. They should provide a detailed interest computation as they conclude the case.

Were HMRC to repay overpayments arising for specific years, then they would add repayment supplement. If a general payment on account is held, then it does not attract repayment supplement but would retain its effective date of payment.