Amounts without an invoice

You will always have to provide some proof, otherwise you will end up with fixed costs. But I don't think that's what you want to add.

If you want to include an expense in your accounts, you need to have some kind of document. If necessary, not an invoice (which is required to recover vAT), but a proof of payment, ticket, etc. Something that states the amounts and what you bought is the minimum a auditor will want to see before accepting an expense in your accounts. Please note that if you want to reclaim vAT, you do need an invoice! If it's just to enter an expense, you can also use a ticket, receipt, proof of payment, etc.