How long from time can you get a refund for small entity

[from MyPatentBar]

The applicant accidentally paid large entity filing fee even though entitled to small entity status.

Can he get a refund and how long does he have to apply?

37 CFR 1.28(a). Refunds when small entity status is later established; how errors in small entity status

are excused. (a) Refunds based on later establishment of small entity status. A refund pursuant to § 1.26,

based on establishment of small entity status, of a portion of fees timely paid in full prior to establishing

status as a small entity may only be obtained if an assertion under § 1.27(c) and a request for a refund of

the excess amount are filed within three months of the date of the timely payment of the full fee.

The three-month time period is not extendable under § 1.136. Status as a small entity is waived for any fee

by the failure to establish the status prior to paying, at the time of paying, or within three months of the

date of payment of, the full fee.