I am 27 can I have sex with an 18 year old

You can, as long as the 18 year old is a willing participant.

But, just because you can, doesn't mean you should.

If she really is OVER age 18 you have nothing to worry about legally. If she is UNDER age 18, then you have something to worry about legally.

18 is Legal I find it funny that you are worried about her age. Just because she says she is 18 does not mean she is. You are taking a gamble if she is not. My guess is you have already did the deed. Now you are worried about it.
Hope everything is OK! 18 is really young for 27 later in years it is not such a big deal but this age well...
Then in Canada where I live legal age of consent is 16 so it is all relative.

"Just because you can do a thing, does not mean that you should." Yeah, that's good advise.

Can refers to ability. Well, of course you can.

May refers to how OK it is, or if you have permission, or if it is legal.

Yes, you may.

Yes. Just make sure she really is first. Look at her ID card or something so you know for sure. There was a guy in my town who got arrested for dating a minor. She swore she was 18, and looked like it. She even told the cops that she lied to him, he still was charged though.

Funny simoneaugie. I love your answer.
She better have given permission. Then they say the average teen female loses there virginity at 13 teen 13 my god!

Yes I know someone that it happened to as well bad news!!