The following are the current rates at September 2012

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Interest on overdue tax

Interest on all unpaid tax is charged at the same rate.

The formula is Bank base rate plus 2.5% which gives a present rate of 3%.

There is one exception: Quarterly instalments of corporation tax bear interest at only 1.5%.

Repayment supplement

Interest on all overpaid tax is payable at the same rate.

The formula is Bank base rate minus 1% but with an overriding minimum of 0.5% which applies at the present time.

Official rate of interest

From 6 April 2010: 4%