Firmware
I forgot my firmware password and I don’t have the original invoice
Question marked as
Then there is no way to remove it.
You can try and contact the place of purchase and see if they are able to give you a copy of the invoice
See:
Set a firmware password on your Mac – Apple Support
If you've forgotten your firmware password
If you can't remember your firmware password, schedule an in-person service appointment with an Apple Store or Apple Authorised Service Provider. Bring your Mac to the appointment, as well as your original receipt or invoice as proof of purchase.
Good luck!