There are two methods:
PayPal issues a receipt to the user, which need to be submitted to Admin as proof of purchase.
Using PayPal imply there are charges and costs to us, in addition to the above fees.
Hence, we add these charges as follows:
We anticipate that all invoice payments are received prior course attendance. However, we have some leeway, which is that a maximum period extending 3 weeks after course complettion is a hard limit, and thereafter, we will initiate penalty charges.
ERCOFTAC Members - Course & Seminar Payment Process