Vehicle data services
Car valuation API integration: part-ex widgets and sell-my-car tools
A car valuation API lets a buyer enter a reg and mileage and get a part-exchange figure on your site or inside the sales process, from cap hpi Black Book, Auto Trader Connect or VDG. We integrate the valuation, the lookup behind it and lead capture, with the condition, mileage and margin rules your sales team use.
A valuation is a lookup with an opinion attached. The reg resolves to a derivative; the derivative plus mileage, age and condition resolves to a figure. cap hpi Black Book is the trade's reference, with trade, retail and forecast values keyed on cap IDs, and pricing on quotation. Auto Trader Connect returns retail, trade and part-exchange valuations, including no-VAT fields, from the same data that drives Retail Check on the Dealer Portal. Vehicle Data Global publishes a Valuations package at £0.203 per lookup pay-as-you-go or £0.157 on subscription, ex VAT (published price, check current). MotorCheck and HPI offer valuations alongside provenance.
The widget is the easy part. What makes a part-ex tool useful is the rules layer: how much to deduct for condition answers, whether to show a figure or a range, floors and ceilings by stock profile, how to treat mileage that disagrees with the DVSA MOT history, and what happens to the lead. A valuation without a lead capture and a CRM push is a free service to your competitors. A valuation that is wildly generous burns the sales team's time. We build the tool around how your appraisers actually price.
Compliance sits underneath. A reg plus a name and email is personal data, so the form needs a lawful basis, a privacy notice and a retention period, and any follow-up email or SMS needs consent or a valid soft opt-in under PECR. If the journey leads into a finance quote, Consumer Duty and FCA CONC financial-promotion rules apply to what the page says next.
How it works
End to end
- 01
Capture reg, mileage and condition
A short form: VRM (validated), current mileage, and three to six condition questions (service history, bodywork, tyres, keys, MOT). Nothing that requires the customer to know their derivative.
- 02
Resolve the vehicle
VRM lookup via cap hpi, VDG or Auto Trader Connect taxonomy returns make, model, derivative, fuel, transmission and a cap ID or Auto Trader derivative ID, which is what the valuation service keys on.
- 03
Call the valuation service
Black Book trade, retail and forecast; Connect retail, trade and PX; or the VDG Valuations package, adjusted for mileage. Cross-check the customer's mileage against the DVSA MOT history and flag discrepancies.
- 04
Apply your rules
Condition deductions, margin, stock-profile floors and ceilings, and the choice of figure versus range. Rules live in configuration your sales manager can change without a developer.
- 05
Capture the lead and push it
The valuation, vehicle and answers go to your CRM or DMS (enquiryMax, Dealerweb, HubSpot, Keyloop, Pinewood, Dragon2000) with the source page and campaign, and the customer gets a written figure with an expiry.
- 06
Audit and refresh
Every valuation is stored with provider, date and inputs so appraisers can see what the customer was shown; cached results expire on a policy that matches the provider's terms and the market.
Deliverables
What you get
- Part-ex or sell-my-car widget styled to your site, with VRM validation
- Valuation service with provider abstraction and caching
- Rules engine for condition, margin, floors, ceilings and figure-versus-range
- MOT mileage cross-check with discrepancy flags
- Lead capture with CRM or DMS push and campaign attribution
- Valuation audit log for appraisers
- Privacy notice wording, lawful-basis record and PECR-compliant follow-up
- Reporting: valuations, leads, conversion to appraisal and to sale
Data sources
Providers we integrate
We are provider-neutral: we pick the source that fits your budget, licensing position and the fields you actually need.
| Source | What it returns | Notes |
|---|---|---|
| cap hpi Black Book (Solera) | Trade, retail and forecast values keyed on cap IDs; CAP codes; New Vehicle Data spec and options; VRM lookup licensed direct from DVLA. | Access via cap Web Services and data files; pricing on quotation. Black Book Cars individual plans include 150 registration look-ups a year (published, check current). |
| Auto Trader Connect valuations | Retail, trade and part-exchange valuations including no-VAT fields, plus taxonomy derivative lookup by VRM or OEM model code. | Part of Auto Trader Connect; integrations must meet Auto Trader's integration fundamentals and partners are certified. Retail Check and Retail Rating are the Dealer Portal equivalents. |
| Vehicle Data Global (VDG) Valuations | Valuation figures alongside the provider's vehicle identity data. | Listed at £0.203 per lookup PAYG or £0.157 on subscription, ex VAT (published price, check current). Per-lookup billing; credits valid 12 months. |
| MotorCheck Valuation API | Private, part-exchange, auction and trade values, plus Vehicle Identity and History Check products. | OAuth2 client credentials, 99.5% uptime SLA, free trial; pricing on request. |
| HPI Vehicle Data API (Solera) | Valuations with provenance: finance agreements, write-off categories, stolen markers, National Mileage Register discrepancies. | Pay-as-you-go to subscription; pricing on quotation. Useful where the part-ex journey needs a provenance check before an offer is firm. |
| DVSA MOT History API | Odometer readings at every MOT since 2005, used to sanity-check the mileage the customer enters. | Free; OAuth 2.0 plus API key; 500,000 requests a day. |
Data quality
Where this goes wrong, and what we do about it
Free-text DVLA model names resolve to the wrong cap ID or derivative, so a base model is valued as the top trim.
Resolve derivative via the valuation provider's own taxonomy lookup from the VRM, and show the customer the derivative before the figure so they can correct it.
Customer-entered mileage disagrees with the MOT history, sometimes innocently, sometimes not.
Pull the last MOT odometer reading, flag the gap, and let the rules engine widen the range or route the lead to manual appraisal.
Registration date is not model year, so a car registered late on the old spec gets valued as the facelift.
Use build-date range and derivative from the lookup, not registration year, when selecting the valuation record.
Imports and NI-registered vehicles return thin data and unreliable values.
Detect import flags and plate formats, and route those to a manual quote rather than an automated figure.
Provider licence and caching: valuations reused beyond the provider's terms, or the same VRM billed on every refresh.
Cache per VRM and day within the licence, record retention, and expire figures on a defined policy.
Vehicle Valuation Tools: common questions
Which car valuation API should a UK dealer use?
cap hpi Black Book if you already price on cap IDs; Auto Trader Connect if Auto Trader is your stock and pricing hub; VDG for a per-lookup option with a published price. The choice depends on which taxonomy your DMS and sales process already speak.
How much does a car valuation lookup cost?
cap hpi and HPI quote per project. VDG lists Valuations at £0.203 per lookup pay-as-you-go or £0.157 on subscription, ex VAT (published price, check current). Auto Trader Connect valuations come through your Connect integration.
Can the widget show a guaranteed offer?
It can show whatever your rules produce, but most dealers show a range or an indicative figure subject to appraisal. The rules engine lets your sales manager set condition deductions, floors and ceilings, and decide when a lead goes to manual quote.
Does a part-exchange form need GDPR consent?
The form needs a lawful basis and a privacy notice, because a reg plus contact details is personal data. Follow-up email or SMS is direct marketing under PECR, so you need consent or a valid soft opt-in and an opt-out in every message.
Can you check the mileage the customer enters?
Yes. The DVSA MOT History API returns the odometer reading at every MOT since 2005. We compare the customer's figure with the latest reading, flag discrepancies and let your rules decide whether to widen the range or route to a manual appraisal.
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Scope vehicle valuation tools for your platform
Tell us your platform, your data provider (if you have one) and what the customer should be able to do. We will come back with a fixed-price scope and an honest view of the data licensing.