HMRC have produced a factsheet which outlines the process for appealing tax decisions to the independent tax tribunal. It applies to tax decisions made on or after 1 April 2009.
A taxpayer has the choice of having a decision reviewed by a different officer from the one who made the decision which is the subject of a dispute, or the taxpayer may have the case heard by an independent tax tribunal. The tribunal is independently heard by expert judges and/or panel members and is administered by the Tribunals Services which is part of the Ministry of Justice.
To appeal to the Tribunal, the appeal must be made in writing within 30 days of the HMRC decision letter or within 30 days of a review decision.
If a decision is in respect of a direct tax matter, then the payment or part of the payment in dispute can usually be postponed until the appeal is settled. Interest will continue to accrue on any unpaid tax that is found to be due when the appeal is settled.
If the decision is in respect of an indirect tax matter, then payment of the disputed tax can be postponed while a review is in progress but the tax must be paid before an appeal can be heard. HMRC may make exceptions to this in cases of hardship.
For full details see here