hey @Richard-Keith and @judy
Here: http://laytheme.com/buy-now.html
theres a faq, it says:
"Where do I get the invoice?
After your purchase you will receive an email by Gumroad that says "Receipt" in the subject. Inside, there is a button to generate your invoice. If you have any problems generating your invoice please write support@gumroad.com."
@Richard-Keith theres no need to have a detailed description about needing an invoice, he/she just needs an invoice