Can I remove Activation Lock on my Mac with a retail invoice?

Your receipt will not be accepted for Activation Lock removal. I can print out a receipt with the device serial number and fancy seal and it means absolutely nothing. Just because someone gave you receipt does not prove the device you bought was not stolen. Return the Mac and get your money back. If they refuse to give you your money back, then you can see why it is important to buy from Apple or Authorized Apple Seller and never make that mistake again.

No. Do not purchase such a Mac.

A a second-hand, Activation-Locked Mac from a dealer who is not an Apple Authorized Reseller? I wouldn't touch that deal with a ten-foot pole, and I very much doubt that Apple would be willing to remove Activation Lock on the basis of that dealer's invoice.

Save your money. Buy elsewhere!

Note that in some countries, the online Apple Store has a Certified Refurbished section.

The discount is usually only about 15% off the original list price – so it's useful to know enough about recent models to be able to tell if that represents a good value. But the refurbishment process is very thorough. The Mac that I'm typing this on right now came from the Certified Refurbished store, and I would not hesitate to purchase a Mac from the Certified Refurbished store again.

Certified Refurbished Products - Apple

Beware of "refurbished" Macs from other vendors, which may be little more than used machines, thrown into a box, without a thorough refurbishment process or a warranty that lasts very long.