The benefits code: beneficial loans: calculation of the cash equivalent: number of whole months
Section 182 ITEPA 2003 For the purpose of the calculation in
EIM26215 months begin on the sixth day of the calendar month.
So a loan made on 7 June and repaid on 15 December of the same tax year is outstanding for five whole months (July to November inclusive). But a loan made on 6 June and repaid on 5 December of the same tax year is outstanding for six whole months (June to November inclusive).