I was sent an invite from a customer recently. He wants me to create a few trial post for him to review prior to engaging me. This will not be paid, I was wondering can he still leave a review on my account without a contract?
No reviews can be left for you without a contract in place.
I strongly advise against doing any "trial" articles. It's against the rules to do any free test work. Do you have sample articles in your profile? If so point those out to this potential client.
Most likely they are trying to get you to work for free and won't be hiring you.
Ok then he can pay you what you think would be a good rate for a few test articles.
He would be able to leave feedback for those. If you feel for any reason that he's going to leave bad feedback I'd tell him you're not interested and stop communicating.
If there is no contract, there is no work, too. If there is no work, there is no feedback, too.
But I don't suggest you work for free. Just send the client your previous works, don't work.