Speaking to BBC Radio 5 Live's Sportsweek programme, Redknapp said: "It's not a major issue.
"It's something that was done between myself and my ex-chairman, away from football, and it really is. well, it's unbelievable, I've got to be truthful.
"I can't comment on it, but it's farcical."
A statement issued last night by solicitors BCL Burton Copeland, acting for Redknapp, read : "Harry Redknapp is extremely surprised and disappointed to have been informed that HMRC intend to institute proceedings against him in the week commencing January 11, 2010.
"We believe that the decision to commence proceedings will, in due course, be shown to have been totally misconceived."
Tottenham last night issued a statement backing the 62-year-old, who has masterminded a change in fortunes for the club since taking charge just over a year ago and taking the club up the Premier League table.
"The club considers this matter to be a private, tax issue which pre-dates Harry's employment with the club and which is not related to football matters," the statement read.
"His position remains unaffected and he has the full support of the club."