Know your real buying costs and maximum bid before you buy
For independent UK dealers and auction buyers. Enter your expected selling price and known costs — BidMargin adds Copart or BCA fees and VAT and shows the most you can bid and still hit your margin.
The calculator is free — no sign-up needed.
BetaFree while in beta — pricing coming soon.
UK registration lookup
Sign in free to fill in vehicle details and see DVSA MOT history from a reg.
Sign in to look up a registrationYour own estimate — BidMargin doesn't value cars.
Auction fees
Known costs
Enter costs you know. The −25 / +25 / +50 buttons only change this calculation; BidMargin never suggests repair costs.
Unforeseen repairs (optional)
Add a safety margin for repairs you can't see yet. Nothing is added until you press Apply. Don't repeat costs already entered above.
No change to max bid.
An applied contingency is saved inside Other, so reports and saved deals match.
Maximum bid
£6,559
Target profit £2,299 · costs £1,700
Based on your selling price and costs. Gross cash profit is before tax and not guaranteed.
Check a bid
Enter a bid to see true cost, profit and margin.
Deal metrics
Enter a bid to see cash cost, profit and return.
Assumes you sell at the expected retail price you entered. Gross cash profit is before tax, overheads and VAT on your sale — it is not net profit and not guaranteed.
Repair scenarios (compare)
Enter how much more (or less, with −) repairs might cost versus your known bodywork and mechanical figures. These are comparisons only — your deal doesn't change unless you press Use. Repairs never go below £0 and Other/contingency is not touched.
Max bid £6,559 · Profit at bid —
Max bid £6,559 · Profit at bid —
Max bid £6,559 · Profit at bid —
BidMargin doesn't diagnose faults or guess repair prices — the figures are yours.
VAT margin scheme (optional)
Notes
Photos
Save this deal first, then you can add photos of the car and the auction sheet.
Frequently asked questions
How do you calculate my maximum bid?
You enter the price you expect to sell the car for, your target margin and your known costs (transport, repairs, MOT, valeting and so on). BidMargin works backwards: the highest bid where the bid, the auction's fees on that bid and your costs still leave your target profit. With Copart or BCA selected it checks the stepped fee schedule penny by penny rather than using a percentage guess.
What do UK car auction fees include?
Usually a buyer's fee that steps up with the hammer price, plus extras such as online bidding or retrieval fees. Copart publishes its fees before VAT, so BidMargin adds 20% VAT to them. BCA's Blue Standard fees are published including VAT, so nothing is added. Optional charges like BCA's V5 handling are only counted if you switch them on.
Are the BCA and Copart fees guaranteed?
No. BidMargin uses the published standard schedules with the version and date shown in the app. Your own account level, the sale or later price changes can make your invoice different. Bids outside the published range get no rating. For other auctions or account rates, use Manual fees.
How is VAT treated?
VAT on auction fees is counted as a cost. VAT on the hammer price is only added if you say the lot is sold plus VAT. Profit shown is gross cash profit before tax — reclaiming VAT and VAT on your own sale aren't modelled. An optional HMRC margin-scheme illustration is available once you confirm eligibility and enter the invoice price.
Does BidMargin give valuations?
No. The expected selling price is your own figure. BidMargin does not provide market valuations, comparable adverts, days-to-sell, finance or stolen-vehicle checks.
Are the DVSA MOT results current?
They come from the DVSA MOT History service when you look up a registration, and are kept for up to 30 days to save repeat lookups. They show past tests only — they don't prove a car is roadworthy today. Always inspect the vehicle.
Do I need an account?
No. The calculator works free without signing up. A free account lets you save deals, use registration lookup, set your default costs and see profit history.