An inmate number is the unique identifier a correctional system assigns to a person in its custody, and it’s the key piece of information you need to send mail, deposit commissary funds, schedule a visit, or confirm where someone is housed. In the federal system, the U.S. Marshals Service assigns an eight-digit register number written as five digits, a hyphen, and three digits.1Federal Bureau of Prisons. Program Statement 5100.08 – Inmate Security Designation and Custody Classification State prisons and county jails use their own formats, but the purpose is the same: making sure the right person is identified in a system where shared names are common.
What an Inmate Number Looks Like
Federal Bureau of Prisons (BOP) register numbers follow a strict pattern: five digits, a hyphen, then three digits, for example 12345-678. The BOP inmate locator calls this the “BOP Register Number” and requires that exact format when searching by number.2Federal Bureau of Prisons. Find an Inmate
State prison systems and county jails each build their own numbering schemes. Some are purely numeric, others alphanumeric, and lengths run from six to ten or more characters. A person held in a county jail and later transferred to a state prison ends up with two different numbers in two different databases. Someone who has done federal and state time will have a number in each system.
Who Assigns the Number and Whether It Changes
In the federal system, the U.S. Marshals Service assigns the register number, not the Bureau of Prisons itself.1Federal Bureau of Prisons. Program Statement 5100.08 – Inmate Security Designation and Custody Classification It is issued during intake after sentencing or commitment. State and county facilities handle assignment through their own booking procedures when a person enters custody.
Once assigned, the number stays with that person for the duration of their time in the system. Transfers between facilities within the same system do not change it. A federal inmate moved from one BOP institution to another keeps the same register number, and the number remains in the system’s records after release. The BOP locator includes records for federal inmates incarcerated from 1982 to the present, not just those currently in custody.3U.S. Department of Justice. Locate a Prison, Inmate, or Sex Offender
Inmate Number vs. Booking Number
These two get confused constantly, and the mix-up matters when you’re trying to locate someone or send money. A booking number is a temporary reference tied to a single arrest event. Arrested three times at the same county jail? That’s three booking numbers.
An inmate number is tied to the person, not the event. It persists across transfers within the same correctional system and stays on file after release. When a facility or online portal asks for an “inmate number” or “register number,” a booking number will not substitute. Using the wrong one can block whatever you’re trying to do.
How to Find an Inmate Number
For federal inmates, the fastest path is the BOP’s online inmate locator. You can search by name using fields for first name, last name, race, sex, and age.4Federal Bureau of Prisons. Federal Inmates By Name If you already have the register number, you can search by that directly.2Federal Bureau of Prisons. Find an Inmate Results show the register number, current facility, and expected release date.
For state inmates, USAGov directs people to contact the relevant state’s department of corrections.5USAGov. How to Look Up Prisoners and Prison Records Most state corrections departments run their own online inmate search tools that work similarly to the federal locator. County jails usually offer search tools through the local sheriff’s office website, though quality and completeness vary widely.
For older federal prison records, the National Archives and Records Administration handles historical requests. Include the person’s name with middle name or initial, date of birth or approximate age at incarceration, race, and approximate dates in prison.5USAGov. How to Look Up Prisoners and Prison Records
What You Need the Number For
Nearly every practical interaction with a correctional facility requires the inmate number, and this is where most families and friends first run into it.
Mail and Money Orders
The BOP requires the inmate’s full committed name and eight-digit register number to be printed legibly on all negotiable instruments and on the outside of the envelope containing them.6Federal Bureau of Prisons. Sending Funds Using USPS Mail missing the register number, or carrying the wrong one, risks being returned or delayed. State and county facilities have similar requirements, with the exact format set locally.
Commissary Deposits
The commissary account is how incarcerated people buy food, hygiene items, and other approved goods. Deposits require the register number. When using Western Union to send funds to a federal inmate, you enter the eight-digit register number without dashes or spaces, immediately followed by the inmate’s last name.7Federal Bureau of Prisons. Sending Funds Using Western Union A typo can send money to the wrong account, and recovering misrouted funds is neither quick nor guaranteed.
Visits
Planning a visit starts with confirming the person’s current facility. The BOP’s visiting information page asks for the inmate register number to look up housing location.8Federal Bureau of Prisons. How to Visit a Federal Inmate You’ll typically need it again on visitor approval paperwork. Video visitation platforms used by state and county systems work the same way.
Other ID Numbers People Confuse With It
An inmate number is only one of several identifiers a person accumulates in the criminal justice system, and the alphabet soup trips people up. These are the ones most often mistaken for an inmate number:
- State Identification (SID) Number: Assigned by a state’s criminal records agency, usually tied to fingerprint submissions. A SID follows a person across all encounters with that state’s criminal justice system, not just one facility.
- FBI Number: A federal identifier assigned when fingerprints go into the FBI’s national database. It links records across state lines but is not tied to any single prison or jail.
- Case Number: Assigned by a court to a specific legal proceeding. One person can have several. This is a court identifier, not a corrections identifier, and it will not work in prison search tools or fund deposit systems.
When a facility, portal, or form asks for an “inmate number,” it wants the number assigned by that particular correctional system. A SID, FBI number, or case number will not substitute.
Does the Number Go Away After Release?
No. The number does not expire or get deleted when someone is released. The BOP’s inmate locator includes records going back to 1982, covering both current and former federal inmates, and a register number remains searchable there after a sentence is completed.3U.S. Department of Justice. Locate a Prison, Inmate, or Sex Offender State systems generally keep similar historical records, with varying depth and public access.
For anyone going through reentry, the number is effectively a permanent part of the record. Background check services that pull correctional data may return the inmate number alongside conviction information.