I have a client who has not been great at keeping their accounting records or even purchase invoices/receipts. I know what the majority of the costs are for as I have credit card statements etc. Would you put the allowable business expenses through the books and take a deduction?. Obviously I cannot claim back the VAT on hotels etc and there is no way of getting duplicate invoices for these. But where a cost is clearly fuel and I can see that it is on the statement would you try and claim back the VAT. I know in practice that I have to have a valid VAT receipt but am wondering the reality in practice when something is clearly for the business.
I would write to the client and let them tell you what they want you to do. It would be them who suffers the comeback, and you need to let them make the decision.
You want to explain that, whilst the statements do provide some evidence of expenses, its not a given that HMRC will accept anything. That said, they probably wouldn't outright disallow everything, just because they were no invoices. Its the risk you take, a) that you would even get an investigation, and b) that you got such a negative inspector that they wouldn't allow any of it.
I would say the VAT was the trickier issue. Again, HMRC can show sense when looking at the situation. They know all fuel has VAT on it... but that doesn't mean they have to allow it.
I'd recommend giving your client the low down, and let them decide whether they want to go for it and hope for the best - to answer you in writing, maybe a letter of representation. If they go ahead and claim, I would make it clear that the only way forward is to keep immaculate records, to a) show that this period was a one off that was learned from, and b) to show how the expenses continued - this might give loose evidence that the claim was legit.