That one is a loaded question in many ways. But, usually the answer to that is a big NO! All too often, once a contract has been signed, the terms have already been legally agreed upon, and are not subject to modification unless both parties agree. In fact, many times the agreement needs to be in writing before a modification is even enforceable. Generally speaking, the best way to avoid pitfalls related to early execution of documents, is to check with your legal counsel before you sign them!