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HMRC internal manual

Inheritance Tax Manual

Assessing: calculating interest: decrease in total tax in IOP cases

Where there is a decrease in the total tax, you can easily include the adjustment in the calculation for the next instalment.

Remember to repay any interest that was paid on the tax that was overpaid (IHTM31611). Remember to repay interest that was overpaid on the balance of tax that was outstanding, and that has now decreased.