Legal Question in Business Law in Pennsylvania

I assume you are talking about the entity number the State Department assigned to you when it filed your LLC documents. If I am correct, then no, you do not need to list your LLC entity number on your contracts with other people. If however, you are talking about your LLC's EIN number, then you may or may not want to list that number on the contract. The EIN is your LLC's social security number. If a client pays you more than $600 per year, that client should issue a W-9 at the end of the year to you. To do that, the client will need your EIN number. Whether you list that number on your contract or in a seperate letter to the client, is a matter of convenience for you. Good luck.