LLC, INC, Corporation on letterhead, bizcards, etc

Not sure if this question has been asked before, but do you have to put the LLC, INC, Corporation, etc on letterheads, business cards, etc at the end of the company name?

I've been trying to find an answer but can't seem to find a satisfactory one.

I've observed that some companies do put the LLC, Inc, Corporation on their business cards and letterheads and some other companies don't. So maybe it's okay to not include it? Are there any business laws that say you have to put your company formation at the end of your company name?

Thanks for your help.

It depends if your business is registered as a single proprietory business, a partnership, or a corporation.

Right, but I've seen for example Company A LLC won't put the LLC at the end of their business cards, or letterhead. So i was just wondering if there were rules about it.

I don't think there are any rules about it. If you don't want to use them, then it's okay, since when applying for a business name, you only write THIS and THAT.. and not THIS INC, or THAT LLC. Just like a doctor, they are not required (or so i think) to write M.D. in their business cards. They just do it, because it makes them more respectable and distinguished.