Quick answer: Before paying for a used Samsung Galaxy, dial *#06# for the IMEI and check it against a stolen and blocked database. Make sure the seller has removed their Google and Samsung accounts so Factory Reset Protection can't lock you out. Then run the Diagnostics tests in the Samsung Members app, check the AMOLED screen for burn-in, test the S Pen on Ultra models and confirm your SIM works. Don't pay until it's set up with your own accounts.
This checklist covers Galaxy S, Galaxy A and Galaxy Ultra phones bought from private sellers or shops. Each step says where to look, what a good result is and which results should end the deal. Settings paths and features were checked against Samsung UK, Google and Samsung Knox support pages in October 2026. Samsung's menus vary slightly between One UI versions, so if a label differs on the phone in front of you, look for the nearest equivalent.
How to find a Samsung IMEI number
Answer first: Samsung UK lists three quick ways to find the IMEI on a Galaxy phone: dial *#06# in the Phone app, open Settings > About phone (it shows the IMEI, model number and serial number), or read the label above the barcode on the box. On older devices you may need to tap Status inside About phone.
Use all three where you can and make sure they match. A Galaxy with dual SIM support will show two IMEIs, one per SIM slot. If the IMEI on screen differs from the box, the box belongs to another phone or the phone's main board has been replaced. Either way, ask questions before going further.
Ask the seller for the IMEI before you meet. You need it for the stolen-phone check in step 2, and an honest seller has no reason to withhold it.
The 11-step used Samsung phone checklist
Step 1: Know who you're buying from
Your legal position depends on the seller. A business must sell goods of satisfactory quality, fit for purpose and as described under the Consumer Rights Act 2015, whether the phone is new or second-hand. A private seller's main duty is that the phone matches the description. Citizens Advice notes they can't misdescribe it but can leave information out. With a private sale, the checks below are your only protection. Our guide to refurbished vs used vs renewed phones covers the differences in detail.
Step 2: Run a stolen and blocked IMEI check
Answer first: Put the IMEI into CheckMEND before you pay. CheckMEND is the buyer's check linked to Immobilise, the free UK property register connected to the police National Mobile Property Register. CheckMEND says its report shows whether a device is recorded as stolen, lost, subject to an insurance claim or blocked by a mobile network.
What the result means: any record of theft, loss, an insurance claim or a network block means walk away. A blocked phone may not connect to UK networks, and a stolen phone can be recovered by police however much you paid. Once you own the phone, register it free on Immobilise.
Step 3: Check the Google account and Factory Reset Protection (FRP)
Answer first: Factory Reset Protection is Google's anti-theft lock on Android phones. Google says that if a protected phone is reset using its buttons (recovery mode), setup asks for the previous screen lock or the Google Account that was on the phone. If you can't provide them, you can't use the device at all. The seller must remove their Google account before resetting.
How to check:
- If the phone is still set up, ask the seller to open Settings > Accounts and backup > Manage accounts, select their Google account and tap Remove account. Samsung UK lists this as the way to remove a Google account.
- Then ask them to factory reset the phone from Settings, not with the buttons. Google notes a reset from Settings asks for the screen lock first.
- After the reset, start setup. If the phone asks you to verify a Google Account that was previously synced to it, FRP is still active.
Red flags: a phone already sitting at a "verify your account" screen; a seller who has "forgotten" the Google password; any listing mentioning "FRP bypass" or "FRP removed". Samsung UK says that if you're locked out by FRP, you can take the device with proof of purchase to an authorised Samsung Service Centre. As the buyer of a locked phone, you won't have the proof of purchase that requires.
Step 4: Make sure the Samsung account is removed too
Galaxy phones can also be signed in to a Samsung account, which links the phone to Samsung's services. Samsung UK says remote actions such as a SmartThings Find factory reset need the device signed in to a Samsung account. The removal steps are the same: Settings > Accounts and backup > Manage accounts, choose the Samsung account, tap Remove account, then sign out with the account password.
What the result means: once both accounts are gone and the phone has been reset, there should be nothing linking it to the seller. If a Samsung account sign-in screen appears during your setup with the seller's email pre-filled, stop. The seller needs to remove it with their password.
Step 5: Check the model number
Settings > About phone shows the model number (it starts with "SM-"). Compare it with the model the seller advertised by searching the number on samsung.com/uk. This confirms you're getting the model and generation you're paying for, and tells you if the phone was made for another market. Imported variants can differ in processor, network bands or software, so check it suits UK use.
Step 6: Check it's network unlocked
Galaxy phones don't show a simple "unlocked" line in Settings the way iPhones do, so test it. Put your own SIM in, or a SIM from a different network to the one the seller used, restart the phone and make a call and use mobile data. If the phone asks for a network unlock code, it's locked.
Ofcom banned UK mobile companies from selling locked handsets from 17 December 2021. Phones bought before that, or abroad, can still be locked, and only the network that locked a phone can unlock it.
Step 7: Run Samsung Members Diagnostics
Answer first: The Samsung Members app, preinstalled on Galaxy phones, includes a Diagnostics feature that tests the phone's hardware. Samsung UK's steps are: open Samsung Members, tap Support, tap View tests, then Test all. Samsung notes you must verify a Samsung account to use Diagnostics.
That account requirement affects timing. Either ask the seller to run Diagnostics while their account is still signed in, before they remove accounts and reset, or run it yourself after setting the phone up with your own Samsung account at the end of the inspection. You can skip individual tests and return to them, or tap a single test to check one function.
Battery: Samsung's support pages describe a battery status test in Samsung Members that reports the battery as Normal, Weak or Bad. Normal is what you want. Samsung describes Weak as reduced efficiency from long-term use, and Bad as significantly degraded, with a Samsung Service Centre visit advised. Some recent Galaxy models also show more battery detail in Settings, but menu availability varies by model and software version, so Samsung Members is the most consistent check.
Step 8: Check the AMOLED screen for burn-in and touch faults
Many Galaxy phones use AMOLED screens (the spec sheet on samsung.com/uk names the display type for each model). Like other OLED panels, they can show burn-in: a faint permanent ghost image of something left on screen for a long time, such as the status bar, navigation buttons or keyboard.
- Display a plain mid-grey image full screen at maximum brightness, then a plain white one. Look for ghosted outlines, especially along the top and bottom edges.
- Check for green or pink tints, dead pixels and uneven brightness.
- Drag an icon slowly around the whole screen, including the curved edges on models that have them, to find touch dead zones.
- Test the in-screen fingerprint sensor by registering your own fingerprint and unlocking several times.
What it means: slight burn-in visible only on a grey test screen is common on older phones and should be reflected in the price. Burn-in you can see in normal use, a line across the display or touch dead zones are reasons to walk away or budget for a new screen. Our Galaxy A-series screen and battery replacement cost guide gives an idea of what that adds.
Step 9: Test the S Pen on Ultra models
Answer first: The Galaxy S22 Ultra was the first Galaxy S phone with a built-in S Pen, and later Ultras keep it. Pull the S Pen out, check the tip isn't worn down, and test writing, hover and Air command. On the Galaxy S25 Ultra, Samsung says the S Pen has no Bluetooth and Air actions aren't available, so don't mark that as a fault.
How to test:
- Remove the S Pen. Air command (the pen-in-a-circle icon) should appear. Open a notes app and write across the whole screen.
- Hover the S Pen just above the screen. A pointer should follow it.
- Push the S Pen back in and make sure it clicks home and the phone registers it.
- On S22 to S24 Ultra, Air actions (such as using the S Pen button as a camera shutter) rely on Bluetooth, so test one if the seller says they work.
A missing S Pen isn't a deal-breaker on its own, but a replacement costs money and should come off the price.
Step 10: Check for Knox warranty tampering
Answer first: Samsung Knox includes a Knox Warranty Bit: a one-time hardware e-fuse that is permanently set if the phone has loaded an unsigned kernel or had a critical security feature such as SELinux disabled. That usually happens when someone roots the phone or flashes custom software. Samsung's Knox documentation says it can't be reversed, and Samsung Pay and work profiles are blocked once it's set.
Ask the seller directly whether the phone has ever been rooted or had custom firmware. Then, once the phone is set up with your account, open Samsung Wallet and start adding a payment card. If Samsung's payment feature refuses to work on an otherwise normal UK Galaxy, treat it as a sign the phone may have been modified, and walk away unless the seller can explain it. A tripped Knox Warranty Bit is permanent, so this phone will never get those features back.
Step 11: Test hardware, look for damage, then set it up as yours
- Cameras: switch through every rear lens and the front camera, tap to focus up close and zoom on telephoto models. Look for blur, black lenses and misted or dusty glass.
- Audio: play audio at full volume through both speakers, record a video and a voice note, and make a test call.
- Buttons: press the side key and volume up and down.
- Charging: plug in a cable and try a wireless charger if the model supports it. Check the port for debris or looseness.
- Connections: join Wi-Fi, pair Bluetooth and, if you use contactless payments, check NFC turns on.
- Body: check for a screen lifting from the frame (a possible swollen battery), bent frames, cracked rear glass and corrosion in the SIM tray or charging port.
- Water resistance: don't rely on it. Once a phone has been opened for repair, its seals may not be the same. Amazon, for example, states refurbished phones on Amazon Renewed are not guaranteed to keep their waterproof seal.
Finally, set the phone up with your own Google and Samsung accounts, confirm your SIM works, and only then pay.
Skip the checklist: shop a tested refurbished Galaxy S23 and see today's price →
Red flags that should end the deal
- A request to verify the previous owner's Google Account, or a seller who can't remove their Google or Samsung account.
- Any mention of "FRP bypass", "FRP removed" or "Google lock removed".
- CheckMEND shows stolen, lost, insurance claim or network-blocked.
- The IMEI from *#06# doesn't match the box or the seller's message.
- A network unlock code prompt when you insert your SIM.
- Burn-in visible in normal use, lines on the screen or touch dead zones.
- Samsung Wallet payments refusing to work, or the seller admitting the phone has been rooted.
- Seller won't meet, won't let you test, or wants a bank transfer only.
Second-hand Samsung phones: unlocked, refurbished or private?
| Where you buy | Your legal protection | Who handles FRP, IMEI and testing | Typical warranty |
|---|---|---|---|
| Private seller | Goods must match the description | You | None |
| Independent refurbisher or shop | Consumer Rights Act 2015 | The seller, then you | Varies; check length and exclusions |
| Amazon Renewed | Consumer Rights Act 2015 plus Amazon's commercial guarantee | An Amazon-qualified supplier | Amazon Renewed Guarantee: 1 year (third-party sellers) |
| Samsung Certified Re-Newed | Consumer Rights Act 2015 | Samsung | Samsung UK: 2 years; Galaxy S25 series only at launch in January 2026 |
Buying from a refurbisher that publishes its checks removes several steps from your list. At The Tech Gadgets, every Galaxy is tested, cleaned, factory reset and signed out of the previous owner's accounts, and unlocked for all UK networks. Product pages state at least 85% battery health on Like New, Excellent and Very Good grades, measured at dispatch. Refurbished phones carry our 12-month warranty for manufacturing defects and functional faults (excluding physical or water damage, electrical damage and battery wear), with 30-day returns. It's still worth running Diagnostics and the screen test when your phone arrives.
Best used Samsung phone to buy
The best second-hand Samsung phone is the newest Galaxy S model your budget allows that still gets software updates and passes the checks above. A newer phone with a healthy battery beats an older Ultra with a weak one. For model-by-model picks, see our best refurbished Samsung phones for 2026. If you want the S Pen, S24 Ultra vs S22 Ultra refurbished compares the two most popular Ultras. Running costs after purchase are covered in the cost to own a refurbished flagship.
Shop refurbished Samsung Galaxy phones with a 12-month warranty →
Frequently asked questions
How do I check a Samsung IMEI number?
Dial *#06# in the Phone app, or open Settings > About phone. The IMEI is also printed above the barcode on the box. Dual-SIM Galaxy phones show two IMEIs. Check that they match, then run the IMEI through a stolen and blocked check such as CheckMEND before buying.
What is FRP on a Samsung phone?
FRP (Factory Reset Protection) is Google's lock that stops a reset Android phone being set up without the previous owner's screen lock or Google Account details. If the seller doesn't remove their Google account before resetting, you may be unable to use the phone at all.
Can a Samsung phone be FRP locked after I buy it?
Yes, if a Google Account previously synced to the phone wasn't removed and the phone is later reset with the buttons. Google says any Google Account previously added and synced can be asked for. Set the phone up with your own account and make sure no old account remains before paying.
How do I check battery health on a used Samsung?
Open the Samsung Members app and run Diagnostics (Support > View tests). Samsung's battery status test reports Normal, Weak or Bad. Diagnostics requires a verified Samsung account, so run it with the seller signed in or after you set the phone up with your own account.
How do I know if a used Samsung phone is unlocked?
Insert a SIM from a different network, restart and make a call. If the phone asks for a network unlock code, it's locked, and only the network that locked it can unlock it. Ofcom has banned UK networks from selling locked phones since 17 December 2021, but older or imported phones may still be locked.
What does a tripped Knox warranty bit mean?
It means the phone has run unsigned or modified software, usually from rooting or custom firmware. Samsung's Knox documentation says the bit is a permanent hardware fuse that can't be reset, and features relying on Knox security, such as Samsung Pay, are blocked.
Is it worth buying a used Galaxy with screen burn-in?
Only if the burn-in is faint, visible only on a plain grey test screen, and the price reflects it. Burn-in doesn't go away, and replacing an AMOLED screen on a flagship Galaxy is one of the more expensive repairs. A refurbished phone with a graded screen is usually better value.