Namecheap has horrendous billing UI with their products, also not PDF so makes it hard for freelancers when you have many domains and your accounts want an PDF. Easiest is a registrar that mails you invoices in PDF.
their billing works just fine, i pay with it all the time.
They support credit/debit cards, bitcoin, and Paypal.
I went with Namecheap especially because of their seamless payment method,
Used to struggle at times paying for my domains with Gandi, etc.
You: "their billing works just fine" [then talking about payments, when I wasn't talking about payments but billing, "The process of sending an invoice (a bill) to customers for goods or services" -Wikipedia]
They have their billing for domains and products spread over several pages, there is not one place in the UI where they have all payments/billing combined, they don't have PDFs as I've stated and they don't sent invoices by email. Their billing UI is horrendous.