Here's the regulatory requirements and Guidance on the Notice timing (emphasis added):
1. Prior to Closing:
Must be delivered to the borrower(s) and to the servicer if applicable, within a “reasonable time”, before the completion of the loan. [§339.9(c)]
2. Reasonable Time:
The regulations do not establish a fixed time period in which a lender must provide the notice. What constitutes a reasonable time will necessarily vary according to the circumstances of the particular transaction. [MPFIG – page 34 and Federal Register /Vol. 74, No 138 – page 35930]
3. Regulatory Guidance:
The Agencies generally continue to regard ten days as a “reasonable” time interval.
[Federal Register /Vol. 74, No 138 – page 35930]
Dan's right. You delivered in a reasonable time, but you don't have the documentation to prove it. I always recommend YOU date the form when you mail it and just ask them to sign it. When they don't (rarely do they sign and return it or bring the copy you sent to closing), you whip out your copy of the dated Notice and have them sign it.
The alternative is to keep a copy of the letter sent with the Notice (dated, of course) to prove when it was mailed.