50 CFR § 86.71
How much time do I have to complete the work funded by a BIG grant?
July 17, 2020
(a) We must obligate a grant within 3 Federal fiscal years of the beginning of the Federal fiscal award year.
(b) We will work with you to set a start date within the 3-year period of obligation. We assign a period of performance that is no longer than 3 years from the grant start date.
(c) You must complete your project within the period of performance unless you ask for and receive a grant extension.