20 CFR §404.1286

1. (a)Subject to the exceptions to the time limitations in §§ 404.1287 and 404.1289, a State is not liable for an amount due under an agreement unless the Commissioner makes an assessment for that amount before the later of the following periods ends:
   1. (1)Three years, 3 months, and 15 days after the year in which the wages, upon which the amount is due, were paid; or
   2. (2)Three years after the date the amount became due.
2. (b)Where the time limitation ends on a weekend, legal holiday or Federal nonworkday, an assessment is considered timely if the Commissioner makes the assessment on the next Federal workday.