"The penalty would be 50% of the value of that advantage and if the taxpayer persisted in appealing on the basis that he was exempt from income tax, that penalty would be payable if the taxpayer lost (and returnable with interest if the taxpayer won)."
“(1) Where - …(c) [the taxpayer] has co-operated” with HMRC, HMRC may reduce the amount of the penalty to reflect the quality of that cooperation”
“(1) providing reasonable assistance to HMRC in quantifying the tax advantage (factor (a)); and (2) counteracting the denied advantage, either by (b) amending the relevant SA return(s); (c) providing the information to HMRC so they can take the relevant corrective action; or (d) by coming to an agreement with HMRC to give up the denied advantage. And where the corrective action is being taken by HMRC, the taxpayer will also “co-operate” if he “allows HMRC to access the relevant tax records to ensure that full reversal of the denied advantage” (factor (e)).”