Knowledge Base

This article explains how to build a car buying website using One Auto API.

It covers each stage of the process—from vehicle identification to lead generation, valuation, and risk management—highlighting the data services and endpoints that make each step possible.

A car-buying site is a website where users can:

1. Enter a vehicle registration number to identify their vehicle
2. Submit their contact details in return for a valuation
3. Receive an estimated valuation
4. Receive a finalised valuation following a detailed appraisal of their vehicle based on images,  service history and checks

Success in this competitive space depends on:

• Fast and accurate data retrieval
• Presenting a competitive estimated valuation 
• Effective risk management (avoiding losses on vehicles with adverse history, or in poor condition)
• Smart automation to reduce operational costs

Goal: Return a vehicle description when the user enters their registration number.

Suggested endpoints:

Vehicle Details from VRM – Vehicle description, import/export/scrapped markers, keeper change history and last v5c issue date.

Vehicle Images from VRM – Car images (monthly licence required)

Best Practice:

Use vehicle details to identify problem vehicles early on.

Professional vehicle images increase trust and boost conversion,  helping you maximise the value of paid search campaigns.

Goal: Capture customer contact details

• Present the vehicle description to verify plate input is correct
• Capture mileage at this stage
• Present a form for name, email, and phone number

Best Practice:

Explain that details are collected to “send a valuation and updates about your offer” and always store explicit consent (GDPR).

Goal: Reduce risk and enhance valuation accuracy

Suggested endpoints:

Salvage Check – Identifies whether the vehicle has been salvaged (insurance write-off, stolen/recovered or unclassified).

Taxi Check – Identifies whether the vehicle has been or is currently licensed as a taxi/private hire vehicle.

Stolen Check – Identifies whether the vehicle is currently listed as Stolen on the Police National Computer (PNC).

Condition Check – Identifies whether the vehicle is an insurance write off with a marker in the MIAFTR database.

Recall Check – Identifies vehicles with outstanding recalls which may take time to resolve before they can be legally sold. 

Best Practice:

Run checks in ascending or order of price, to minimise cost.  

Use both Condition and Salvage checks to maximise identification of insurance write-offs. 

Goal: Provide a competitive but risk-adjusted price estimate

Suggested endpoints:

Brego Current Valuation – 3 retail and 3 trade values,  with coverage of cars,  light commercials, motorcycles and leisure vehicles.

Brego Desirability Rating – 0-100 rating indicative of market demand.

Percayso Valuation – 5 retail and 1 trade value, including expected days-to-sell.

Percayso Market Demand – 0-100 rating indicative of market demand.

Marketcheck Price Predictor Premium – Retail price,  including expected days-to-sell with current and recent comparable listings.

UKVD Valuation – 7 retail, private and trade valuation points for cars.

Best Practice:

Decline or downgrade values depending on your risk tolerance for:

• Imports
• Exported/scrapped markers
• Vehicles with a change of keeper in the last 6 months
• V5C re-issued recently (indicates a back-dated keeper change)
• Salvaged vehicles
• Insurance write-offs
• Outstanding recalls
• Prior use as a taxi or private hire vehicle

Provide a banded valuation (e.g. £7800-£9100) to balance competitiveness and risk

Apply adjustments based on your sales history and market demand to customise your valuation stance.

Rule logic example:

{
  “if”: [“keeper_change_last_6_months”, “v5c_issue_last_6_months”],
 “then”: {“risk_flag”: “recent_purchase”, “valuation_multiplier”: 0.75}
}

Goal:  Build trust to conclude a purchase,  while managing risk.

Suggested endpoints:

Digital Service History – Manufacturer digital service history for 30+ brands.

Finance Check – Finance data provided by Experian.

High Risk Check – High risk markers added to assets at risk of unauthorised sale or disposal.

Best Practice:

Ask users to upload vehicle photos to evaluate condition. 

Build a relationship with the customer as you work with them to finalise a valuation of their vehicle. 

Check the digital service history,  to confirm whether the car has been maintained to manufacturer standards – and adjust your valuation accordingly. 

Check for third party interests (Finance and High Risk)

One Auto API helps you build a full-stack car-buying experience that:

• Delivers a frictionless user experience
• Screens for adverse history and risks
• Delivers tailored, data-driven valuations
• Enables scalable buying operations with human oversight
• Optimises data costs by using cheaper checks early in the process,  postponing more costly in-depth checks until later in the process when volumes are lower.