In or out?

I wonder whether readers can provide some guidance on the following scenario.

Let us say that I had a client who ceased to trade (and therefore deregistered for VAT) on 31 December 2012 and that he always used the flat rate scheme while he was in business.

If the trader’s accountant had invoiced him for final accountancy services on 30 December 2012 the client cannot claim input tax on the fee because at that time he was using the
scheme.

However if the accountant had invoiced him for the work on 31 December 2012 he could claim input tax because he is deemed to have left the scheme on 30 December so normal VAT rules apply for input tax incurred on this date.

What would be the position if the accountant invoices the client on say 31 March 2013 – after having concluded...