Being de-arrested is uncommon enough that most people have never heard the term, and significant enough that it is worth its own page. It means the police released you from arrest without charge, at the scene or shortly afterwards, and recorded that they had done so.
Why it matters evidentially
The lawfulness of an arrest is judged on what the officer knew and believed at the time. A de-arrest does not automatically mean the original arrest was unlawful: grounds can genuinely exist and then genuinely evaporate a few minutes later when someone produces a receipt or a witness speaks up.
But it does two useful things. It fixes the end of the detention precisely, and it forces a written record of why the arrest ended. Where that recorded reason is that the grounds were never made out, the force has documented the central issue in the claim in its own words.
What to ask for
The custody record if you reached custody, the officer's pocket notebook entries, the incident log, and any body-worn video. Body-worn footage is routinely deleted on a retention schedule measured in months, so a request made early gets material that a request made late does not.
You can ask for material held about you through a subject access request, which is free.
How long you have to bring a claim
Publishing a general figure here would be worse than publishing nothing, because a reader who relies on the wrong one loses their claim outright. Get your own position checked, and do it early rather than late.
The free routes, before any claim
A complaint to the force costs nothing and does not stop you claiming later. If the force's answer does not stand up you can apply for a review, and across all forces reporting, 24.5% of completed reviews found the force's own outcome was not reasonable and proportionate.
The three routes, and what each one gets you.
Start with your force
Complaint handling, review outcomes and stop and search practice vary enormously between forces. Every force has its own page here with its own figures.