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UK Auction Finance Calculator

Win the lot on Saturday and the clock starts immediately: 10% down in the room, the balance in 28 days. This calculator shows exactly how much cash you need to complete — deposit, stamp duty, bridging interest, lender and broker fees — and how many days you have left to arrange it.

  • Built around the 28-day contract
  • 2026 stamp duty bands + surcharge
  • Works on your phone in the room
  • Free to use

Work out your cash to complete

Fill in what you know. Every field has a sensible auction default already in it, so you can get a usable answer in under a minute and refine it afterwards.

1 · Property & bid details
£

The hammer price, between £50,000 and £5,000,000.

Completion is 28 days later on a standard contract.

10% is the auction standard. This money is already gone — and is what you lose if the finance does not land.

£

Optional — unlocks the profit and ROI figures on the exit card.

2 · Loan requirements
£

Leave blank to use the balance after your deposit.

%

Auction bridging typically runs 0.55% – 1.5% per month.

Retained interest is held back from the advance, so it lands on your day-one cash.

%
%
£
£

Both sides — yours and the lender's.

3 · Stamp duty position

Company and buy-to-let purchases always attract the surcharge.

If you already own property, the 5% additional dwelling surcharge applies.

4 · Where should we send the breakdown?

Your results appear on screen straight away. We also keep them on file so a bridging specialist can talk you through the numbers before the 28 days run out.

By submitting you agree we may contact you about auction finance. We never sell your details — see our privacy policy.

How the auction finance calculator works

1

Enter the hammer price

Add the price you bid, the deposit you paid in the room and the date of the sale.

2

Set the bridge

Term, monthly rate, how the interest is paid and the arrangement fees your broker has quoted.

3

See your cash to complete

One number, fully broken down, plus the days you have left before the notice to complete lands.

Auction finance questions, answered

How much cash do I need to complete an auction purchase?

On a standard 28-day auction contract you need the 10% deposit on the day, then stamp duty, lender and broker arrangement fees, valuation and legal fees, plus any retained interest at completion. On a £250,000 purchase that is typically £55,000 to £70,000 once the deposit is included. This calculator works out your exact figure.

How quickly can auction finance be arranged?

A bridging lender can usually issue terms the same day and complete in 10 to 14 working days, provided the valuation is instructed immediately and your solicitor already has the legal pack. Leaving it past day 14 of the 28 is what puts the deposit at risk.

How much will a bridging lender actually lend on an auction lot?

Most bridging lenders cap at 70-75% of the purchase price (or of the valuation, if it comes in lower). A 10% auction deposit therefore leaves a gap of roughly 15% of the price that you must fund yourself or cover with additional security.

What stamp duty will I pay on an auction property?

Residential SDLT is charged in bands: nothing to £125,000, 2% to £250,000, 5% to £925,000, 10% to £1.5m and 12% above that. A 5% surcharge is added for second homes, buy-to-let and company purchases. The calculator applies the 2026 rates automatically.

What happens if my finance is not ready in 28 days?

The seller can serve a notice to complete, charge interest at the contract rate, and ultimately rescind and keep your 10% deposit. That is why the countdown, not the interest rate, is the number that matters most on an auction purchase.

Is retained, serviced or rolled-up interest better?

Retained interest is deducted from the advance, so it increases the cash you need on day one but leaves nothing to pay monthly. Serviced interest keeps your day-one cash lower but needs monthly income to cover it. Rolled up interest is settled in full when the loan is redeemed.