12 CFR § 792.24
Can NCUA charge me interest if I fail to pay my bill?
November 10, 2020
NCUA can assess interest charges on an unpaid bill starting on the 31st day following the date of the bill. If you fail to pay your bill within 30 days, interest will be at the rate prescribed in 31 U.S.C. 3717, and will accrue from the date of the billing.