Not entering the full purchase invoice – method

Then you simply enter the portion that is business-related and calculate this price yourself. Your proof of purchase only counts as evidence. This does, of course, include vAT; you cannot simply discard the vAT. But you mention an invoice. Was it actually issued to your sole proprietor using your vAT number? If so, I don't think my advice is correct, and you should contact Support.

Or perhaps you should sell it to yourself, as stated in this article in the learning center: https://dexxter.be/zakelijke-purchases-in-boekhouding-voor-privegebruik/