Hi Sander,
Going to answer in English, hope that's ok :)
I'm planning to open an Etsy shop for digital products as well!
My plan to deal with the challenge you described is the following:
e.g. sell 100 eur, fees 20 eur, but etsy bank deposit of only 70 eur instead of 80
- register the full revenue of 100 eur as: debit accounts receivable, credit revenues
- register the 20 eur fees as: credit accounts payable, debit expenses
- register the 70 eur cash payment that Etsy processed as: 70 debit cash, 20 debit accounts payable, 90 credit accounts receivable
So at the end of the month you'll have:
Assets = 80:
Cash 70
Accounts Receivable 10
Liabilities = 0:
Accounts Payable 0
Equity = 80 (Profit & Loss Result):
Revenues 100
Expenses -20
Hope this helps,
Monica
(for context: I am not a chartered accountant, but I have an educational background in the field, and work in management accounting for a large corporate firm)