The Used-Phone Checklist: What to Verify Before You Pay

A used phone can be the smartest purchase in tech: the same hardware for hundreds less, because someone else paid the new-phone premium. It can also be a locked, blacklisted, or quietly water-damaged brick that no refund policy will save you from. The difference between those two outcomes is rarely luck — it's about ten minutes of checks, most of which cost nothing. Work through this list in order. The first items are deal-breakers you can verify from your couch, before you've driven anywhere or sent anyone money. The rest are hands-on tests for when the phone is actually in front of you.

Check the remaining support window before anything else

This is the step almost every used-phone buyer skips, and it's the one that decides whether the deal makes sense at all. A phone's real lifespan isn't set by its battery or its glass — it ends the day the manufacturer stops shipping security updates. A used phone has already burned through part of that window. A three-year-old phone from a brand that promised five years of updates has two years of safe life left, no matter how flawless it looks in the photos.

So before you even message the seller, get the exact model name and look up its end-of-support date on our end-of-support tracker. Then do the per-month math. As a hypothetical: $250 for a phone with two years of support remaining works out to roughly $10 per month of safe use. The same $250 for a phone with eight months left is over $30 a month — worse value than many new budget phones. Price per month of protected use, not price alone, is the number to compare.

Two quick follow-ups once the phone is in hand: confirm it's actually receiving updates (our two-minute settings check shows you where to look), and confirm the model number in Settings matches what was advertised. Sellers sometimes list the wrong variant — and variants can have different support windows and different network bands.

Make sure the phone is the seller's to sell

A phone that's still tied to someone else's account, or flagged as lost or stolen, is worthless — not “fixable later,” worthless. Three checks close this off:

• Match the IMEI. Dial *#06#on the phone to display its IMEI (the device's serial number for networks). It should match the IMEI shown in Settings and, on many phones, the one printed on the SIM tray or the original box. A mismatch means parts-swapped or misrepresented hardware — walk away.
• Run a blacklist check.Put that IMEI into the CTIA's free Stolen Phone Checker or your carrier's own device checker. If the phone was reported lost or stolen, or has unpaid financing, carriers will refuse to activate it. No price is low enough for a phone that can't get service.
• Verify the activation lock is off. On an iPhone, the previous owner must sign out of their Apple ID and turn off Find My. On Android, their Google account must be removed, or Factory Reset Protection will demand their password after any reset. The only proof that counts: watch the seller perform a full factory reset in front of you, then set the phone up past the first sign-in screen beforeyou pay. If it asks for the previous owner's password, hand it back.

That factory reset also protects you in the other direction — it wipes the seller's data, so nobody later claims you walked off with their accounts.

Read the battery health number, not the seller's adjective

“Battery lasts all day” is an opinion. The phone keeps an actual number. On an iPhone, open Settings → Battery → Battery Health & Charging and read the maximum capacity. On newer Android phones, battery health lives under Settings → Battery; on older ones you may only get an estimate from a diagnostics app. As a rough guide: 90% and above is healthy; the high 80s is fine but worth a small discount; below 80% means the battery is at the end of its useful life and a replacement — typically $50–$100 at a repair shop — should come off the price. Our battery health explainer covers what that percentage really measures and why 80% is the line that matters.

The ten-minute hands-on test

Bring your own charging cable and, if you can, your own SIM card. Then, on the freshly reset phone, test everything that's expensive to fix:

• Screen. Pull up a plain white image, then a plain black one, and look for dead pixels, discolored patches, and OLED burn-in (ghost outlines of a keyboard or status bar). Drag an icon slowly around the edges of the screen to catch dead touch zones.
• Cameras. Take a photo and a short video with every lens, front and back. Check that focus locks quickly and the flash fires. Haze or spots that appear in every shot mean moisture or damage inside the lens.
• Speakers and microphones. Play music at full volume and listen for crackle. Record a voice memo and play it back. If your SIM is in, make a call both on and off speakerphone — that exercises both mics.
• Buttons and biometrics. Press every physical button, toggle the mute switch if there is one, and enroll your own fingerprint or face during setup to confirm the sensor works.
• Charging port. Plug in your cable and confirm the phone charges. Nudge the connector gently — if charging cuts in and out, the port is worn, dirty, or corroded.
• Radios. Join a Wi-Fi network, pair a Bluetooth device, and with your SIM in, load a web page over mobile data.
• Water damage. Pop the SIM tray and look inside the slot for the liquid contact indicator: white or silver is clean, red or pink means the phone has been wet. Any green or white crust in the charging port is corrosion. Either one is a walk-away, because water damage fails weeks later, not on test day.

Carrier fit, and why where you buy matters as much as what

A perfect phone that can't get a signal on your network is still a bad buy. Ask whether the phone is carrier-unlocked, then verify it two ways: your own SIM should make calls and pull data on the spot, and the IMEI should pass your carrier's bring-your-own-phone compatibility checker. Be careful with international variants of US models — they can look identical while missing the 5G bands your carrier uses.

Then weigh the venue. A marketplace or refurbisher with real buyer protection — returns, a warranty, a money-back guarantee — costs a bit more and is worth it for most people, because every check above gets a safety net. A cash meetup is cheaper with zero recourse: once you drive away, every problem is yours. If you do meet in person, use a police-station safe-exchange zone or a busy public place, in daylight. And if you're deciding between a private seller and the refurbished market specifically — grading tiers, warranties, what “renewed” actually promises — that's a different calculation, covered in our guide to whether refurbished phones are safe.

Negotiate with the numbers, and know when to walk

Everything you just checked doubles as leverage. Battery under about 85%? The cost of a replacement comes off the price. Support window shorter than the listing implied? Fewer months of safe use means the phone is worth less per month — you can put the asking price and the support runway into the true-cost calculator and show the seller the math. Missing charger, cracked back, scuffed frame: all ordinary, all negotiable. Sellers respond better to specifics than to haggling for its own sake.

Some things, though, aren't discounts — they're exits. Walk away if:

• the seller won't factory reset in front of you, or wants to do it “after payment”;
• the phone is still signed into someone's account, for any reason, with any story;
• the IMEI is blacklisted, has unpaid financing, or doesn't match the tray or box;
• the price is dramatically below market — stolen phones are priced to move fast;
• you're being rushed, or discouraged from testing;
• the liquid indicator is tripped or the port shows corrosion;
• security updates have already ended, or end within a few months, unless the phone is nearly free.

The one date that outranks everything else

The hands-on tests tell you whether the phone works today. The support window tells you how long it's worth owning — and it's the only item on this list you can't fix with a repair shop or a discount. So make it the first check and the last: before you shortlist any used phone, look up its end-of-support date on the end-of-support tracker. If the runway is long, every other item on this checklist is worth your ten minutes. If it isn't, you already have your answer, and you didn't have to leave the couch to get it.