“2–– (1) A penalty is payable by a person (P) where P makes an unauthorised issue of an invoice showing VAT. (2) P makes an unauthorised issue of an invoice showing VAT if P— (a) is an unauthorised person, and (b) issues an invoice showing an amount as being value added tax or as including an amount attributable to value added tax. (3) In sub-paragraph (2)(a) “an unauthorised person” means anyone other than— (a) a person registered under VATA 1994, (b) a body corporate treated for the purposes of section 43 of that Act as a member of a group, … 6B–– The penalty payable under [paragraph] 2 … is— (a) for a deliberate and concealed act or failure, 100% of the potential lost revenue, (b) for a deliberate but not concealed act or failure, 70% of the potential lost revenue, and (c) for any other case, 30% of the potential lost revenue. … 20–– (1) Liability to a penalty under [paragraph] 2 does not arise in relation to an act or failure which is not deliberate if P satisfies HMRC or (on an appeal notified to the tribunal) the tribunal that there is a reasonable excuse for the act or failure. …”