How has IRIS calculated the clients' loan benefit?

IRIS has calculated the loan benefit amount as follows: 1. The average amount of the loan is multiplied by the official rate of interest for the year. If the benefit was not available all year then the sum is apportioned accordingly. The average value of the loan is calculated as follows: (amount outstanding at start of fiscal year + amount outstanding at end of fiscal year) / 2. 2. Any interest paid by the borrower will also be deducted but this only applies for low interest (type 2) loans. Note that details of the official rate of interest can be found here: https://www.hmrc.gov.uk/rates/interest-beneficial.htm Both methods are equally correct, the precise method is normally used if the maximum amount of the loan outstanding during the tax year is higher than the amount outstanding at the start and end of the tax year.