You can find someone's inmate ID number with the official locator for the system holding them. Use the BOP inmate locator for federal prison, the state corrections department's search for state prison, the sheriff's jail search for county jail, and the ICE detainee locator for immigration detention. The quickest way of all is often to ask your loved one, or check the return address on a letter they've sent you.
The number matters. Mailrooms rely on it, and mail with a missing or wrong number is a common reason prison mail gets returned. Here's what the number is called in each system and where to find it.
First, figure out which system they're in
The ID number depends on who's holding your loved one:
- Federal prison: people convicted of federal crimes, and some people awaiting federal trial
- State prison: people serving state sentences, usually longer ones
- County or city jail: people awaiting trial, serving short sentences, or waiting to be moved
- Immigration detention: people held by ICE, who may be in an ICE facility or a county jail
If you're not sure, start with the jail in the county where they were arrested. If they've been sentenced, check the state system next, then the federal one.
Federal prison: the Register Number
Everyone in Federal Bureau of Prisons custody has an 8-digit Register Number, written as five digits, a hyphen and three digits, like 12345-678. It stays the same for that person.
To find it, search the BOP inmate locator by first and last name. The locator covers people in federal custody from 1982 to the present. The results show the Register Number and the facility where they're held.
A few tips:
- If the locator shows a Residential Reentry Management office, they're in a halfway house or on home confinement. The BOP doesn't publish those addresses.
- "Released" or "Not in BOP custody" means they aren't in a federal prison now.
- Write the number with the hyphen, exactly as the locator shows it.
Our guide to sending photos to federal prison covers the rest of the federal address format.
State prison: a state number with its own name
Every state corrections department gives people its own number, and each one has its own name and format. Some examples from our facility pages:
- Texas: TDCJ Number
- California: CDCR Number, which mixes letters and digits
- New York: Department Identification Number (DIN), written like 98-A-0004
- Florida: DC Number
- Pennsylvania: Inmate Number, two letters and four digits, like AB1234
- Ohio: Inmate Number, a letter and six digits, like A555555
- Michigan: MDOC Number
- North Carolina: OPUS Number
- Georgia: GDC ID
State corrections departments offer an online search on their official websites, usually labeled "inmate search," "offender search" or "incarcerated individual lookup." Search by name, and the result shows the number and current facility. Our state pages, like New York and Pennsylvania, show how each system wants the number written on the envelope.
Make sure you're on the state's official site, which usually ends in .gov. Third-party lookup sites can be out of date.
County or city jail: the booking number
Most jails use a booking number, sometimes called a booking ID, inmate number or jail ID. The key difference is that a booking number usually changes every time someone is booked. An old number from a past arrest won't work.
To find it, look for an inmate search or "who's in jail" page on the sheriff's office or jail website. Search by name, and the result usually lists the booking number. If there's no online search, call the jail during business hours.
You can also use VINELink, a national service that many states and counties use for custody status updates. It can tell you whether someone is in custody and where. You can sign up for alerts if they're moved or released, which is helpful because people in jail move often. Read more in jail vs. prison mail differences.
Immigration detention: the A-Number
Everyone in ICE custody has an Alien Registration Number (A-Number), 8 or 9 digits, often written with an "A" in front. It's on their immigration paperwork, including the top right corner of the Notice to Appear.
Use the ICE Online Detainee Locator to see where they are. ICE says the best search uses the A-Number and country of birth. If you don't have the A-Number, you can search by name and country of birth. The locator doesn't show anyone under 18, and it only shows people in custody now or released in the last 60 days.
If your loved one is held in a county jail for ICE, the jail may want its own booking number on mail instead of, or in addition to, the A-Number. Our guide to sending photos to someone in ICE detention explains more.
If you can't find them
Don't panic. Common reasons include:
- They were just arrested. It can take time for a new booking to appear online.
- Their name is spelled differently in the system, or listed under a legal name, middle name or hyphenated last name. Try variations.
- They've been moved to another county, a state prison intake center, or a federal facility.
- They've been released.
If a search turns up nothing, call the facility you think is holding them, or wait for your loved one to call you. They can give you their number and the exact way to write it.
Write it exactly as the facility does
Once you have the number:
- Copy every letter, digit and hyphen.
- Use the name the facility has on file, not a nickname.
- Put the number where the facility wants it, usually on the first line next to the name.
- Check it again before every order, especially for jail booking numbers.
How InmatePics helps
When you send photos through InmatePics, we tell you which ID number the facility needs and how it should look. For federal prisons, we can look up the Register Number for you, and we check the BOP locator to confirm the name and facility before we mail. We address every envelope the way the facility requires.
Frequently asked questions
Is an inmate ID number the same as a Social Security number?
No. It's a number the prison, jail or agency assigns. Never put a Social Security number on an envelope.
Does the ID number change if they're moved?
A federal Register Number stays the same, and state numbers usually stay the same within that state's system. Jail booking numbers often change with each new booking, and a move from jail to state prison means a new state number.
Can I send mail without the ID number?
Some facilities may deliver it, but many return mail without a correct number. It's always worth finding it first.
Once you have the number, find their facility and send photos.
