The loan remuneration structure was considered above board for the years it was used until HMRC clamped down following the bankruptcy of Rangers FC, which had been operating a similar scheme.
This led to widespread action and the process was outlawed, but HMRC also applied the law to previous cases and pursued people who used a loan payment scheme as far back as 1999.
As a result of the Morse Review the loan charge now only applies to cases from 2010 onwards, with those who settled for years before this date entitled to a refund.
Steve Packham, spokesperson for the Loan Charge Action Group, said: "It is clear that HMRC are failing to properly honour this and are making the process onerous, confusing and off-putting.
"They are making people jump through unnecessary hoops just to reclaim money they are legally due back, which is a disgrace."