I used the old stand in line at the Post Office method.
10 min for 4 certified envelopes.
fourth in line.
Certified is not even needed if you use priority.
Scans are scans these days. Certified is a waste of money. And Registered is only really for very liquid securities. Hardly anyone uses that any more.
It's a complete waste of money to certify a tax return.
If you want to create a payment record just use your credit card.