In Francois Berrier v HMRC [2014] TC03584 a taxpayer not only suffered tax penalties for omitting income from his return, he was ordered to pay HMRC's tribunal costs. He or his adviser withheld evidence and mislead the tribunal.

Mr Berrier, was granted a £25,000 employee loan by his employer Nomura. Under the terms of his employment the loan was "forgiven" (written off) after one year in employment. He declared the loan write off in the wrong year on his 2009/10 tax return, using the wrong section of his return and so that it was not taxed as earnings. He failed to declare the write off in the actual year it was as earnings together with £833 in interest benefit of the loan on his 2010/11 SA return.
HMRC found his actions to be careless and gave prompted disclosure of these inaccuracies. With the maximum reduction for the quality of his disclosure.
He appealed against his penalties.

The tribunal found that Mr Berrier's employer had provided him with details on how the loan should be taxed with his employment offer. However these details were omitted from the taxpayer's bundle. These showed that Mr Berrier was (or reasonably ought) to have been aware as to how the Loan was taxed.
The taxpayer was careless but was allowed a discount in penalties for 25% for special circumstances: the loan was returned, albeit in the wrong year. HMRC was not asked to suspend the penalties.

For omitting evidence from the Bundle the taxpayer's representative was found to have acted improperly, unreasonably or negligently in the conduct of the appeal for the purposes of Section 29, Tribunals, Courts and Enforcement Act 2007.
In addition either the taxpayer or his representative acted unreasonably in bringing or conducting the proceedings for the purposes of Rule 10(1)(b) of the Tribunal Rules. The representative had signed the appeal form when he was not a qualified solicitor and had not been formally appointed by the taxpayer.
Rule 11(7) defines a "legal representative" as being a person authorised to conduct litigation under the Legal Services Act 2007 (eg a solicitor).