When do you disclose you have a license?

[John Paul]

In the state of PA you must disclose you have a license if you have personal interest in a property.  Is it required when you first meet or before any negotiations take place?

[Johnny Hastings]

In Wisconsin you have to disclose upon first contact with the seller or their agent. It also has to be in writing. 

Not sure how close PA is to that, but a quick web search should turn up an answer.