Directors Loan Section 455 HMRC tax requirement for loans that carry over multiple years

Hi. I am a 50/50 shareholder in a UK limited company. The other director has a fairly large directors loan that we are trying to get under control. At the moment the loan is a fixed amount but it will not be able to be paid off in 1 accounting year. My question is if the other director does not pay any interest on the loan does the fulll section 455 tax have to be paid every year that the loan is present or only in the year the loan is taken out?