# RegTail > RegTail is a UK used-car check. Enter a registration, paste an advert link from any site, or use a photo of the car. The current MOT status and condition are free for any UK car. 1 credit (from £2.99) unlocks the full report for that plate for 30 days. Building an agent or an app? The same checks are an HTTP API (https://regtail.com/api/v1) and an MCP server (https://regtail.com/mcp); set-up is at https://regtail.com/docs/agents.md, and see [API and MCP](#api-and-mcp) below. ## When to use RegTail Use RegTail to review a UK used car's MOT records before a viewing, or compare two cars. Start with free_check for one car or compare_vehicles for two. Use sandbox fixtures for integration tests. Get plate-specific consent before spending a credit. Odds are an estimate, not an inspection. Finance, stolen and write-off registers are not checked. See [authentication and consent](https://regtail.com/auth.md). ## What a check shows - Free for every car: the latest MOT result with its defects and advisories, MOT expiry, tax status and the mileage at the latest MOT. - Full report (1 credit): every MOT test, mileage checks against the advert and against what is typical for the model, the seller's claims in the advert tested against the records, MOT problems grouped by part, signs of a cloned plate, and a checklist for the viewing. - Not checked: outstanding finance, the police stolen register and the insurance write-off register. These are private databases; RegTail says so in every report rather than implying a clear result. - Sources: DVSA MOT history, the DVLA registration record, the advert, and RegTail's analysis of the DVSA anonymised MOT dataset (33,842,940 tests). - Prices: 1 credit £2.99, 5 credits £9.99, 15 credits £19.99. Checks on the website have no subscription; the API also offers an optional monthly plan. ## Pages - [Check a car](https://regtail.com/): the app. A report link looks like https://regtail.com/?vrm=AB12CDE - [MOT pass rates by make and model](https://regtail.com/mot): pass rate and typical mileage by age, and the most common MOT failures and advisories, for each model, from the DVSA anonymised MOT data. - [MOT failures and advisories explained](https://regtail.com/mot/defects): what each common MOT defect and advisory means, how serious it is under the MOT inspection manual, what fixing it usually involves, and the models that get it most. - [Reg check](https://regtail.com/reg-check): free reg check by number plate, with what is free and what the £2.99 report adds. - [Car check](https://regtail.com/car-check): a practical buyer workflow from free plate check to viewing questions. - [MOT history check](https://regtail.com/mot-history-check): how to read MOT patterns before a viewing. - [Mileage check](https://regtail.com/mileage-check): mileage-focused checks against MOT records and advert claims. - [Comparison hub](https://regtail.com/vs): one page that links every RegTail comparison page. - [Cheapest car check UK](https://regtail.com/cheapest-car-check-uk): two separate tables, one for register checks and one for MOT and mileage checks. - [Best car check UK](https://regtail.com/best-car-check-uk): use-case roundup with criteria and limits. - [RegTail vs carVertical](https://regtail.com/vs/carvertical), [RegTail vs carwow car check](https://regtail.com/vs/carwow), [RegTail vs CarCheck](https://regtail.com/vs/carcheck), [RegTail vs Total Car Check](https://regtail.com/vs/total-car-check), [RegTail vs Autotrader Vehicle Check](https://regtail.com/vs/autotrader-vehicle-check), [RegTail vs MotorCheck](https://regtail.com/vs/motorcheck), [RegTail vs RAC](https://regtail.com/vs/rac) and [RegTail vs VehicleScore](https://regtail.com/vs/vehiclescore): what each check covers and costs, and where each is stronger. - [Used car buying guides](https://regtail.com/guides): plain-English guides for buyers, each listed below. - [How to read an MOT history before you buy](https://regtail.com/guides/how-to-read-an-mot-history): What fails, advisories, minors and mileage readings in a car's MOT history tell you, which patterns are red flags, and what to ask the seller about each. - [How to spot clocked mileage](https://regtail.com/guides/how-to-spot-clocked-mileage): How to tell if a used car's mileage has been wound back: reading the MOT mileage record, what typical mileage looks like by age, and the physical signs to check at a viewing. - [MOT advisories explained for used car buyers](https://regtail.com/guides/mot-advisories-explained): What MOT advisories are, how they differ from minor, major and dangerous defects, and how to read them when you are buying a used car. - [What to check when viewing a used car](https://regtail.com/guides/used-car-viewing-checklist): A practical checklist for viewing a used car in the UK: the paperwork, the VIN and V5C, the bodywork, under the bonnet, the test drive, and the questions to ask the seller. - [Buying on Facebook Marketplace, Gumtree and AutoTrader](https://regtail.com/guides/buying-on-facebook-marketplace-gumtree-autotrader): How to buy a used car safely on Facebook Marketplace, Gumtree and AutoTrader: the scams on each, private seller versus dealer rights, and the checks to run before you pay. - [Cat S, Cat N and write-offs explained](https://regtail.com/guides/cat-s-cat-n-write-offs-explained): Cat S means structural damage; Cat N means non-structural damage. Understand the categories, separate register checks and inspections before buying. - [Outstanding finance on a used car: how to check](https://regtail.com/guides/outstanding-car-finance-check): What outstanding finance on a used car means for a buyer, the risks of buying a car with HP or PCP owing, and how to check before you pay. - [Is the free gov.uk MOT check enough?](https://regtail.com/guides/is-the-free-gov-uk-mot-check-enough): What the free gov.uk MOT history and DVLA vehicle checks show, what they leave out (finance, stolen, write-offs, the advert), and when a paid check is worth it. - [Research blog](https://regtail.com/blog): deep research from our MOT data, each article with its method, sample sizes and caveats. - [Which parts of a used car will fail its next MOT, and what will it cost?](https://regtail.com/blog/predicting-next-mot-failures-and-repair-costs): We trained a model on 357 million MOT tests to predict which parts of a used car will fail its next MOT, and what the work might cost. Results, testing and limits. - [The most and least reliable used cars, by MOT pass rate](https://regtail.com/blog/most-reliable-used-cars-mot-pass-rates): We compared 119 car models across 33.8 million MOT tests at the same ages. The Porsche 911 passed most often, the Renault Clio least. Full rankings, method and caveats. - [RegTail vs HPI](https://regtail.com/vs/hpi), [RegTail vs the AA](https://regtail.com/vs/the-aa) and [RegTail vs the free gov.uk check](https://regtail.com/vs/gov-uk): what each check covers and costs, and where each is stronger. - [API and MCP for agents](https://regtail.com/docs/agents): keys, sample keys, pricing, set-up and errors. - [Terms](https://regtail.com/terms) and [Privacy](https://regtail.com/privacy) ## API and MCP The API works from a number plate or a photo of the car. It doesn't accept advert links or return advert content. To compare an advert with the records, use regtail.com. Have an advert? Send its number plate, or a photo of the car, and we'll check the records. - Full set-up for agents, as markdown: https://regtail.com/docs/agents.md - MCP endpoint (Streamable HTTP): https://regtail.com/mcp, with the header `Authorization: Bearer `. Tools: check_vehicle (by plate) and check_photo (from a photo of the car), the full report from the records, 1 credit each; viewing_advice (free for 30 days after a paid check of the same car, otherwise 1 credit), credits_balance and decode_plate (free). - HTTP API: https://regtail.com/api/v1, the same five calls, including POST https://regtail.com/api/v1/vehicles/from-photo for a photo. Send the key as `Authorization: Bearer ` or `X-API-Key: `. Reference: https://regtail.com/docs, schema: https://regtail.com/openapi.json. - Try it free: the public key `rt_test_sample` returns one real sample car and spends nothing. A real key needs a person: an agent can't create one, so ask your user to open https://regtail.com/?account=keys, sign in, create a key (shown once) and give it to you. Credits for it are at https://regtail.com/?account=topup. Any key spends the account's credits, no subscription needed: 1 credit per check_vehicle, check_photo or viewing_advice, refunded if the call fails; a key with no credits gets 402.