There is an official way to do this. The Ministry of Justice runs a service called Apply to find a prisoner's location, covering prisons in England and Wales, and anyone can use it. Two conditions catch people out: you need more than a name, and the person you are looking for has to agree to their location being shared.
What you need before you start
The service asks for the prisoner's name, including any other name they may have used, and then either their date of birth or age or their prisoner number. A name on its own is not enough, which is the first place applications fall down — and if you do not have a date of birth, an approximate age is accepted, so a rough answer is better than leaving it blank. If anyone else in the family has already had a letter, the prisoner number will be printed on it, and that is the single most useful thing to track down before you start. Solicitors cannot use the public form at all and have a separate email route to the Find a Prisoner team.
Everything else about the application is straightforward. The difficulty is not the form; it is the two conditions below.
The part people are not expecting
The prisoner has to give permission for their information to be shared.
That is worth sitting with for a moment, because it is the reason a lot of applications come back without an answer, and it has nothing to do with paperwork. Somebody may not want a particular person to know where they are. Somebody newly in custody may be ashamed, or frightened, or simply not thinking clearly in the first week, and a request for consent arriving in that fortnight can get a different answer from one arriving a month later. The service is not designed to override any of that. It also will not distinguish, in what comes back to you, between consent being refused and the person not being found — which is why an unsuccessful application tells you much less than it feels like it does, and why it is worth trying the other routes below rather than treating it as an answer.
The second thing to plan around is time. GOV.UK says you will get a reply within four weeks. In a situation that feels urgent, four weeks is a long time, and it is the main reason it is worth trying the other routes below in parallel rather than waiting.
Start the application
The form is on GOV.UK under Apply to find a prisoner's location. Search for it by name rather than following a link from elsewhere — there are sites that charge for help with free government services, and this is one of the areas where they operate.
It covers English and Welsh prisons only. Scotland and Northern Ireland run their own prison services and are not included.
Once you know where they are, the next question is usually what the calls will cost.
What to do while you wait, and if it comes back empty
Several situations look like "cannot be found" and are actually something else.
They may not be in prison yet. People held after arrest are in police custody, not prison, and people appearing at court may be moved the same day. In the first days after a court appearance the location can change more than once.
They may be in Scotland or Northern Ireland. Different services, different routes.
They may write first. In practice this is how most families find out. Post from a prison carries the establishment's details, and someone newly received is usually able to make a call in the first day or so — PSI 49/2011 requires governors to make local arrangements for a call within the first 24 hours of reception, precisely so people can tell their family where they are.
They may not have consented. If you have reason to think that is what has happened, pushing harder through official channels will not change it. Somebody the person does trust may be the better route.
It is also worth knowing what you cannot do from the outside once you have found them: you cannot ring in. The prison phone system does not accept incoming calls at all. Contact starts with them ringing you, or with a letter.
Once you know where they are
Two things follow quickly, and both take a few days.
Your number will not work until it is on their approved contact list. Numbers are submitted by the person in prison, not by you, and GOV.UK is clear that the list is checked by security when someone first arrives, so it may take a few days before they are able to call. Under PSI 49/2011 a prisoner on a call-enabling regime can hold up to 20 social numbers — how the phone system works covers the process in more detail, including what the checks involve.
Visits are booked separately, through the prison, and usually require a visiting order. The establishment's page on GOV.UK is the place to check its own arrangements, which vary. If cost turns out to be what limits the calls once they start, the questions families ask first is the place to start rather than a comparison site.
If the calls turn out to be the expensive part, a landline number changes the rate they are charged.
Where to get help from someone who does this daily
If you are getting nowhere, or you simply want to talk it through with someone who is not an official, the Prisoners' Families Helpline is free, independent and run by the charity Pact. It exists for exactly this — the practical questions in the first weeks, from people who have heard them all before.
The Prison Reform Trust advice guide is the clearest plain-English summary of the rules on contact, written for families rather than for staff. NICCO is the national network for children and families affected by imprisonment, and is the right place to start if children are involved.
Frequently asked questions
The questions people ask most when someone has gone into custody.
Can I find out which prison someone is in without their permission?
No. The official service requires the prisoner's permission before their location is shared.
How long does the prisoner location service take?
GOV.UK says you will get a reply within four weeks.
Does it cover Scotland and Northern Ireland?
No. It covers prisons in England and Wales only; Scotland and Northern Ireland have their own prison services.
Can I ring the prison to ask?
Prisons will not generally confirm whether someone is held there, for the same consent reasons. The official application is the route, and the switchboard is for genuine emergencies.
Not knowing where someone is, is its own kind of distress, and the system is not built to move at the speed of that feeling. The application is worth starting today; so is the assumption that a letter or a first call may well beat it.
The monthly plans, and what each one includes, are set out here.