Why compare used cars by reg?
When you're choosing between two similar cars, the adverts rarely help. Both will be “well looked after”, both will have “full service history”, and the photos will be taken on a sunny day. The official records tell a more honest story. Every MOT since 2005 is held by DVSA, with the mileage, the result and everything the tester noticed. Put two cars' records next to each other and differences that were invisible in the listings become obvious.
PlateWise does that for you in one screen. Enter both registrations above and you'll see their MOT status, tax, ULEZ estimate, pass rate, advisories, recurring problems and mileage side by side, with the stronger figure in each row highlighted. A short summary at the top puts it in plain English, for example: “Car A has the better MOT record; Car B has lower mileage.”
What the comparison shows
| Row | What it tells you | Highlighted when |
|---|---|---|
| MOT status | Whether each car can legally be driven today | It's valid rather than expiring or expired |
| Tax status | Taxed, untaxed or SORN, from the DVLA | It's taxed |
| ULEZ | Whether it's likely to meet London's emission standard | It's likely compliant and the other isn't |
| MOT pass rate | Share of tests passed first time or on retest | It's higher |
| Total advisories | Items testers flagged as needing attention | It has fewer per test |
| Recurring issues | Problems flagged at two or more MOTs | It has fewer |
| Mileage | The last odometer reading on record | It's lower |
| Average miles per year | How hard the car has been used | It's lower |
| Mileage anomalies | Readings lower than the one before | It has none and the other does |
We compare advisories per test rather than in total, because a ten-year-old car has simply had more MOTs than a five-year-old one. Comparing totals would always favour the newer car, even if it had been neglected.
Reading the result: what matters most
Not every row carries the same weight. When the summary flags something like an expired MOT, a car that's untaxed or a drop in recorded mileage, deal with that first. Those are the issues that can turn a bargain into a problem.
Recurring issues beat a single fail
A car that failed one MOT on a blown bulb and has passed cleanly since is usually a better bet than one that passes every year but carries the same corrosion or suspension advisory each time. Repeated advisories suggest a problem that has been noted and never fixed. Our guide to MOT advisories explains which ones to worry about.
Low mileage isn't always better
A car that has done very few miles can suffer from its own problems: seized brakes, flat-spotted tyres and perished rubber. A steady, average annual mileage with a clean MOT history is often a healthier sign than an unusually low figure. What you really want to rule out is mileage that goes down between tests, which can point to clocking or a replaced instrument cluster. See how to check if a car has been clocked.
Compare like with like
The comparison works best for cars of a similar type and age. A city car and a seven-seat diesel will naturally show different mileage and wear. If you're choosing between very different vehicles, use the comparison to check each car's history is clean rather than to pick an outright winner.
Guidance, not a guarantee
An example comparison
Imagine two eight-year-old hatchbacks at the same price. Car A has done 62,000 miles and Car B 48,000. On mileage alone, Car B looks like the better buy. The comparison tells a different story:
- Car A has passed every MOT first time, with an average of one advisory per test, and nothing that repeats.
- Car B has failed twice, averages three advisories per test, and has had “corrosion to brake pipes” and “suspension arm bush worn” at each of the last three tests.
- Both are taxed, both have a valid MOT and both are likely ULEZ compliant.
The summary would read: “Car A has the better MOT record. Car B has lower mileage, by 14,000 miles.” In practice, Car B's repeated brake pipe and suspension advisories point to work that's been put off for years, and it's likely to need it at the next test. Car A's extra miles have clearly been well looked after. Unless Car B's seller can show those jobs have now been done, Car A is the safer choice.
That's why we show the reasons, not just a winner. The highlighted rows tell you where each car is stronger; your judgement, an inspection and the seller's answers decide which matters more.
How to compare MOT history step by step
- Note both registrations from the adverts. Most listings show the plate in a photo even when it isn't in the text.
- Enter them above as Car A and Car B, then press Compare. It takes a few seconds.
- Read the summary first, then scan the highlighted rows to see where each car is stronger.
- Check the mileage chart. Both cars' readings are drawn on one timeline, so you can see which has been driven harder and whether either line ever dips.
- Open each full report to read every advisory word for word. That's where you'll find questions to ask the seller.
On any vehicle report you can also press Compare with another car to start a comparison with that car already filled in as Car A.
Questions to ask the sellers afterwards
The comparison often raises a few specific questions. Good ones to ask include:
- “The last two MOTs mention worn brake discs. Have they been replaced since?”
- “The mileage dropped between those two tests. Do you have paperwork explaining why?”
- “The MOT runs out next month. Will you put a fresh one on it before I collect?”
- “It's showing as untaxed. Is it currently SORN, and why?”
A seller with nothing to hide will usually have straightforward answers and receipts. If the answers are vague, that tells you something too.
Comparing vans and motorbikes
The comparison works for any vehicle with an MOT history, including vans and motorbikes. For vans, pay particular attention to average annual mileage, since a van used for multi-drop deliveries can cover two or three times the miles of a typical car.
Is it free?
Yes. Comparing two vehicles is free, with no sign-up, and you can run as many comparisons as you like within a fair use limit. We don't store the registrations you compare against your name, and they're removed from page addresses before anything is sent to analytics.