Readers' forum: Trying to help

I act on behalf of a client who provides advertising services to the small business sector and her priority is to keep her clients happy. She secured a 12-month contract worth £60 000 plus VAT for a building company and the director initially asked her to raise an advance tax invoice for the full value of the contract. She issued the invoice but he then decided that he wanted monthly invoices instead. These would be for £5 000 plus VAT because he paid her monthly. My client obliged but the invoice duplication has now come to light and HMRC has assessed my client for £12 000 of additional output tax and issued a deliberate not concealed error penalty for 35% of the tax underpaid. 

This seems harsh because my client has not gained from the arrangement but simply duplicated her paperwork. She accounted for output tax on the...