This might be a very stupid question regarding tax return and self employment, so prepare for it :)
Remember - your customers are buying from Gumroad, not from you, so we send them invoices.
If I am not the one generating the invoice or having the customer details. How do I justify my earnings for the tax return with HM Revenue & Customs here in the UK?
I was always told all I have to do is show them my customers invoices, but... what if I don't have?
Can I just show them a printed version of each of the transactions in my bank account where I'm receiving the benefits?