Purchase by a private person – no separate account

I have a private stock from which I sometimes need items for my self-employed in secondary occupation. I understand that I can buy from a private person, but I am a bit confused about how to enter this in Dexxter.

Currently, I enter everything as “purchase from a private person”, but I can’t upload an invoice for this, can I?

As my turnover is not very high, I currently also use my private account as a professional account. So no transaction takes place.