The word "form" is what I am getting at.
If it goes in an envelope (letter or legal-sized)- then NO FORMS are needed, right? Birthday cards/ Holiday cards - don't need forms, do they?

What I need to know is can I mail a small (flat) bubble envelope WITHOUT any forms?? Without "claiming" anything? (if I keep it flat and use my postage meter at home.

Steve's answer suggests YES I CAN. (if under a pound and "flat"
Stan's suggests NO I CAN'T.

And Spain is different. I had to actually CHANGE MY TAPE to mail to Spain (repackaged right there on the counter.)