RM2604 | Issuing a manual payable order: Calculation of supplement
From HM Revenue & Customs · Repayment Claims Manual
When you have decided the relevant time and the tax month you can proceed to use thesupplement ready reckoner table provided. The table gives you the interest factors toapply for calculating supplement.
To record your calculation for the claimant prepare form R22 and keep a carbon copy forthe file.
To calculate
work out the difference between the factors for the relevant time and the end of the tax month
multiply the overpayment by the result.
When you have calculated the amount of supplement due