Because Bobbigmac checks in here from time to time: Will it ever be possible to receive an invoice from Picworkflow if I buy credits? My tax office in Germany is not happy, when I say I paid xx euros for keyword and other services, but I can not prove it. An Email would suffice as bill. Best regards, röde-orm

Paypal files the transaction receipt in your Paypal account when you make any purchases through them.
This receipt should contain all the required information for taxes. I don't know specifically about Germany but it's enough for UK taxes.