Interim managers and other freelance consultants expecting a tax refund could be in for a long wait.
That's the view of accountants and business advisors PFK, which has also warned there may be no interest added to the payments.
An announcement from HMRC regarding the delays id due to be issued shortly, the company said.
It claims there is a backlog of claims due to a new, clandestine operation in HMRC's Bristol office that involves manual security checks on claims to ensure they are not fraudulent.
PFK says that the service is confusing, as when a refund is listed as being due on the Government's self-assessment portal it makes no reference to the checking system.
It added that the fact there is no facility for telephoning HMRC can also make it more difficult for people to ascertain the progress of their application.
John Kennedy, tax investigations partner at PFK, is reported as saying some taxpayers are effectively being treated as if they have made false claims, perhaps as a knock on effect of the problems with MP's expenses.
Separately, HMRC recently apologised for a fault on its website that stopped many users from being able to download P60 forms.