It is very common for the taxpayer to believe that they can attend a hearing and produce documents that assist their case on the day. The rule is that all evidence will be allowed to be used unless there are exceptional reasons why not.
Therefore, even if HMRC have not seen any evidence until the day of the hearing, it is still likely to be allowed in unless they need more time to consider and find evidence to challenge it.
Some advisors suggest that the taxpayer should hold on to key evidence to actually prevent HMRC the time needed to properly challenge it. This will not work and you will begin a hearing with the real possibility that the evidence will be thrown out, and the Tribunal Judge will not be very impressed with you either way. It is not a good start to a hearing.
Our advice is to ensure a proper review of the case is undertaken as soon as possible and to serve detailed witness statements and exhibits at the earliest opportunity. This extends to statements you will make in oral evidence. Too often, things are said when the taxpayer is being cross-examined that are not in a witness statement. It opens you up to arguments that you are making your evidence up as you go along and your honesty could be called into question. Everything you want to say should be in a witness statement and this comes, in part, through knowing what questions you might get asked in cross-examination. We have written a sperate article on cross-examination questions and giving evidence at Tribunal.
Finally, make sure you have all the witnesses you need at the hearing. If your case, for example, is that your accountant made a mistake on your VAT return, but that you provided all the necessary material for a correct return to be submitted, get the accountant to the hearing, and with a witness statement from them confirming this, if possible. If you have a colleague or friend that can support your case, get them to the hearing.
It is possible to force witnesses to attend and you would need to make a separate Application to the Tribunal so that a Court Order could be issued for them to attend the hearing. You will need to explain in detail why they should be there and have some evidence that proves they will assist your case and that they are refusing to attend.