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HMRC internal manual

Business Income Manual

Averaging: postponement of payment of tax and interest

Where the individual is required to make payments on account of Income Tax and the payment on account is increased because of averaging then the individual may be able to make a claim to reduce the payments on account. See SALF303.

If averaging results in a repayment, any repayment interest that may be due is calculated by reference to the later year. The online SA Manual chapter elaborates on this at SAM110070.