MPEP § 2595
The following forms are suggested when submitting a maintenance fee or establishing a fee address for maintenance fee purposes. "Maintenance Fee Transmittal Form," Form PTO/SB 45; and "‘Fee Address’ Indication Form," Form PTO/SB/47.
Form PTO/SB/125 ("Request for Customer Number") may be used to request a customer number. Form PTO/SB/66 ("Petition to Accept Unintentionally Delay Payment of Maintenance Fee in an Expired Patent (37 CFR 1.378 (c))") may be used to file a petition under 37 CFR 1.378 (c).
PTO/SB/45 Maintenance Fee Transmittal Form 
PTO/SB/45 Privacy Act Statement 
PTO/SB/47 Fee Address Indication Form 
PTO/SB/47 Privacy Act Statement 
PTO/SB/125A Request for Customer Number 
PTO/SB/125B Request for Customer Number 
Privacy Act Statenment 
PTO/SB/66 Petition To Accept Unintentionally Delayed Payment of Maintenance Fee in an Expired Patent (37 CFR 1.378(c) 
PTO/SB/66 Page 2 
PTO/SB/66 Page 3 
PTO/SB/66 Privacy Act Statement 