Almost all of my accounts are commercial, mostly shops, I never keep copies of my receipts for them, never have, and I've been looked at in depth on 2 occasions by the Inland revenue too, and I've never had a problem.
I print out my own receipts/invoices, and use them as required.
I do have a handful of accounts where I keep records and signed copies of invoices for proof of whether or not they have paid me or not should a dispute arise, in particular, those that have to be sent off to a head office for payment.
Were I VAT registered it would be another matter altogether, then it would be an absolute necessity to have copies of everything.
I have even had the Inland Revenue call me to confirm whether or I clean this shop or that for xxxx? Because they have decided to check up that the receipts being offered by the shop/business are genuine and accurate.
I was supposed to be working by now!
I'm off!!
Ian