Net sale proceeds comparison
Estimated net proceeds after mortgage and sale-cost assumptions.
Net proceeds
House Part Exchange Calculator UK
Compare a new-build house part exchange offer with an open-market sale, including estate-agent fees, sale costs, onward purchase tax, and mortgage impact.
Your Results
House Part Exchange
Part exchange net proceeds£125,000Offer less existing mortgage
Vs open market-£13,438Open-market route ahead after costs
Estimated new mortgage£286,250£1,707 per month
Part exchange trade-off
Offer discount compared with fees and costs avoided.
Amount
Part Exchange Comparison
Market value assumption£325,000
Part exchange offer93.8% of market value£305,000
Offer gapDiscount versus market value£20,000
Estate-agent fee avoided1.3% of market value£4,063
Sale and moving costs avoided£2,500
Net difference after costs-£13,438
Onward Purchase
New home price£425,000
Estimated purchase taxStandard England/NI SDLT estimate£11,250
Cash deposit entered£25,000
Mortgage if using part exchange£1,707 per month£286,250
Mortgage if selling open market£1,627 per month£272,813
Assumptions
Calculation notes
- House part exchange schemes are commercial offers, not formal valuations. Compare more than one valuation where possible.
- This model does not include incentives, reservation fees, mortgage-product fees, developer extras, survey issues, chain risk, timing value, or negotiation strength.
- Purchase tax uses current England and Northern Ireland SDLT assumptions only; use the Stamp Duty Calculator or professional advice for final liability.
Offer comparison
How the part-exchange trade-off is assessed
The comparison is designed to show whether certainty, avoided costs and incentives make up for a lower developer offer.
Open market versus PX
The calculator compares a realistic open-market sale route with the part-exchange offer route.
It deducts selling costs from the open-market case, then compares the net difference against avoided estate-agent costs, speed, certainty, chain risk and any developer incentives entered.
Comparison pathopen-market value - selling costs -> net open-market proceeds; PX offer + avoided costs/incentives -> adjusted PX value
Lower-offer scenario
Example: lower offer but fewer moving costs
- Open-market value: GBP 250,000
- Part-exchange offer: entered by user
- Selling costs and incentives: entered by user
Result: The result shows whether the convenience and avoided costs offset the lower part-exchange offer.
A part-exchange offer can be rational even if it is lower, but only if the certainty and avoided costs are worth the gap.
When the gap may be worth it
- The result is most useful when the open-market value is realistic, not optimistic.
- Mortgage affordability, onward purchase price and developer incentives should be checked separately before accepting.
Content reviewed: 7 September 2026.
Guide
House Part Exchange Calculator UK notes
Model whether a house part exchange offer looks worthwhile by comparing net proceeds, fee savings, convenience discount, onward purchase costs, and estimated mortgage payments.
Review the calculation notes where rules, tax years, thresholds, or eligibility affect the result.
FAQs
House Part Exchange Calculator UK FAQs
What is the House Part Exchange Calculator UK for?
Model whether a house part exchange offer looks worthwhile by comparing net proceeds, fee savings, convenience discount, onward purchase costs, and estimated mortgage payments.