How to Check a Used Phone Before You Pay
Three checks decide whether a second-hand phone is a deal or a brick: the IMEI blocklist, the account lock, and a reset done in front of the seller.
A second-hand phone at two-thirds of the price is a fair deal or a brick, and the difference is usually decided in the ten minutes before you hand over the money. Not by inspecting the screen — by checking three things the seller cannot talk you out of.
[[answer]]Check the IMEI against a blocklist, confirm the device is not tied to someone else's account, and make sure it is not locked to a carrier you do not use. A phone that passes all three can still have a tired battery; a phone that fails any one of them is worth nothing.[[/answer]]
The three checks, in order of how badly they hurt
Account lock. The worst outcome. On iPhone it is Activation Lock, tied to the previous owner's Apple account; on Android the equivalent is Factory Reset Protection. Neither is removable by a repair shop, whatever the shop says. A locked device is a paperweight that looks exactly like a working phone until you reset it — which is why sellers of stolen phones are always happy for you to try everything except a reset.
Blocklist. A phone reported stolen gets its IMEI blocked, and in most countries that block applies to every local network. The handset works on wi-fi and nowhere else. This is the check people skip because it takes a website and a number they have to ask for.
Carrier lock. The mildest of the three and the most common in cheap imports. The phone works, but only with one operator's SIM. Sometimes it can be unlocked officially and free, sometimes not at all.
[[steps]] Get the IMEI from the device, not from the box :: Dial *#06# on the phone itself. A box, a sticker or a screenshot proves nothing — those travel separately from the handset. Check it against a blocklist :: The GSMA device check and most national carrier lookups take the number and answer in seconds. Reset the phone in front of the seller :: This is the moment the account lock appears, if it exists. A seller who refuses a reset is telling you the answer. Sign in with your own account :: If it goes through, the previous owner's account is genuinely detached. Put your SIM in and make a call :: Catches carrier lock and a dead modem in one step. Check the warranty status by serial :: Apple and Samsung both publish a checker. It also confirms the model year against what you were told. [[/steps]]
What the IMEI can and cannot tell you
The IMEI is the handset's own identifier, distinct from the SIM and from the number. Checking it against a blocklist answers exactly one question: has this device been reported stolen or lost to a database that the checker can see. That is genuinely useful and genuinely limited.
It will not tell you whether the phone was stolen yesterday and not yet reported, whether it was taken in another country whose registry the checker does not cover, or whether the account lock is active — that last one lives with the manufacturer, not in any IMEI database. The GSMA publishes how the registry works, and reading it makes clear how much depends on someone having filed a report.
The reset is the real test
Everything else can be argued about. A reset cannot: either the phone comes up asking for the previous owner's account, or it comes up as new. Do it standing there, on the seller's charge, before any money moves.
A phone that fails this test is somebody else's loss as well as your near-miss — [[post:stolen-phone-what-to-do-first-hour|the hour after a theft]] is what decides whether the device ends up on a marketplace at all.
The excuses are a genre of their own — "the data will be lost", "it takes an hour", "I'll reset it at home and send it to you". The first is the point, the second is untrue on any phone made in the last decade, and the third is how the money leaves without the phone arriving.
Buying from a distance
Everything above assumes the phone is in your hands. If it is not, the checks that survive are the IMEI lookup and a video call where the seller dials *#06# and resets the device while you watch. Photographs prove nothing at all — a photo of a screen with an IMEI is a photo of someone else's screen as easily as their own.
Marketplace protection is worth more than any of this if the platform offers it. Payment outside the platform "to save the fee" removes the only mechanism that can get your money back, which is why it is always the seller's idea.
[[faq]] Can a blocked IMEI be unblocked? :: Only by the person who reported it, through their carrier, and only if the report was a mistake. There is no legitimate service that removes a block for a fee. Does a factory reset remove Activation Lock? :: No. The lock is tied to the previous owner's account, not to the data, and survives any reset done without their credentials. The seller says the phone is "clean, just no box" — is that a problem? :: A missing box is normal for a used phone. A missing willingness to reset it is not. Is a phone with a carrier lock worth buying? :: Sometimes, if the discount reflects it and the carrier publishes an unlock procedure. Never on the promise that "any shop can unlock it". What if I already bought a locked phone? :: Contact the seller first — with an account lock, only they can remove it. If they are unreachable, the platform's protection is the remaining route; a repair shop is not. [[/faq]]
The short version
Ten minutes of checking separates a good deal from a total loss, and the ten minutes are all before payment. IMEI from the device itself, a blocklist lookup, and a reset performed in front of you — a seller with a clean phone has no reason to object to any of it.
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