Final answer:
An engagement letter can be modified after being signed, if all parties agree to the changes and follow a formal amendment process, making the original statement false.
Step-by-step explanation:
The assertion that it is not possible to modify an engagement letter once it is signed by all parties is false.
An engagement letter, which outlines the terms and conditions of a business agreement, can be modified post-signature if all involved parties agree to the changes. This typically requires a formal amendment process, with each party's signature to confirm their acceptance of the new terms. It is not uncommon for circumstances or stipulations to change, necessitating revisions to an initial agreement. Therefore, flexibility is built into contract law to allow for such modifications.