Legal Question in Legal Ethics in California

The term you added does not become part of the contract until agreed to by all.

I agree by Mr. Selik. If the other party has signed the agreement, and then you change it, they have not been afforded the opportunity to accept your changes.

This is also not the appropriate category for this question. This question belongs in the general civil or business law category.

Legal ethics and professional responsibility has nothing to do with your question. This category is for questions pertaining to the rules and laws governing how lawyers practice and their obligations to their clients, other attorneys and the courts.

To answer your question, however, the answer to what you specifically ask is "no." However it may result in you having no contract at all. If they sent it to you signed, you changed it, signed it and sent it back, there is no contract. If they sent it to you unsigned, you changed it, then sent it back and they signed it, you have a contract, but if you failed to call the change to their attention they might or might not have grounds to get out of it. You only have a contract that is sure to be valid if both parties sign it after your change, and both know about the change, OR they sign it, you change it, you sign it AND they do something confirming they agree to the change.