Part Exchange on a New Build: How It Works and Whether It's a Good Deal

How Part Exchange Works in Practice

Part exchange (PX) is a mechanism through which a new build developer agrees to purchase your existing home as part of the transaction for your new property. Rather than selling your current home on the open market and using the proceeds as your deposit, you "trade" your existing property against the new build purchase price.

The mechanics are straightforward: the developer has your existing property independently valued, makes you an offer (typically 90–95% of the surveyed market value), and if you accept, agrees to purchase your home on completion of the new build. You pay the difference between the two prices, either from savings, remortgage, or a new mortgage on the new build property.

The primary appeal is certainty and speed. You are not dependent on finding a buyer for your existing home, avoiding a chain, or managing the timing risk of two simultaneous transactions. For buyers in slow local markets, or those in properties that are difficult to sell quickly (unusual construction, top-floor flats, rural locations), part exchange eliminates significant risk.

The Discount: What Developers Actually Offer

Part exchange offers are almost universally at a discount to open market value. Developers justify this on commercial grounds: they take on the risk of holding and reselling your property, pay estate agent fees on the sale, and carry the financing cost of owning your home until they can sell it.

The typical discount ranges from 5–10% below the surveyed market value. This can represent a significant sum. On a £300,000 property, a 7% discount is £21,000 — money you would not sacrifice if you sold privately.

Before accepting a part exchange offer, get at least two independent estate agent valuations of your existing property. Compare those valuations to the developer's offer. If the developer's offer is more than 5% below the lower of your independent valuations, you should seriously consider whether the time saving justifies the financial cost.

Also factor in what you save by not selling conventionally: estate agent fees (typically 0.9–1.5% plus VAT of the sale price), conveyancing costs, and EPC costs are all avoided in a part exchange. Net the savings against the discount to reach your true cost.

Eligibility and Common Restrictions

Part exchange schemes are not available on all new build developments or all plots within a development. Developers set their own eligibility criteria, which typically include:

**Minimum and maximum value ratios.** Most PX schemes require your existing property to be worth no more than 70–75% of the new build purchase price. Developers are reluctant to hold large assets on their books when the primary transaction is relatively small.

**Property type restrictions.** Flats — particularly ex-local authority or high-rise flats — are routinely excluded. Properties with non-standard construction (timber frame, concrete panel, steel frame) are also typically excluded, as are properties with significant structural defects, short leases (below 70 years), or any legal complications.

**Geographic restrictions.** Some developers will only accept properties within a defined radius of the new build site, to manage the logistics of managing the eventual resale.

**Condition requirements.** The developer's surveyor will inspect your property. If significant repair work is needed, the developer may either reduce their offer further or decline PX altogether.

Get the eligibility criteria for your specific developer's PX scheme in writing before you invest time or money in the process.

Tax and Legal Considerations

Part exchange transactions involve two simultaneous conveyancing transactions: the purchase of your new build and the sale of your existing home. Both transactions must be structured carefully to ensure that Stamp Duty Land Tax (SDLT) is calculated correctly. The SDLT on your new build purchase is calculated on the new build price minus the agreed PX value — but only where the two properties are being conveyed simultaneously and the SDLT return accounts for this correctly.

If you own additional properties, the 3% SDLT surcharge applies to the new build purchase. This is the case even in a PX transaction where you are effectively replacing your main residence, unless the existing property is legally completed on the same day or before the new build completion.

Take specialist conveyancing advice from a solicitor experienced in new build PX transactions. The timing of the two completions and the structure of the SDLT return require careful coordination.

When Part Exchange Makes Sense

Part exchange is genuinely attractive in several scenarios: when you have an unusual property that would be slow to sell conventionally; when you are in a chain that has collapsed repeatedly; when speed of move is more important to you than maximising sale proceeds; or when the new build developer is offering an enhanced PX scheme — occasionally developers will offer at 100% of market value to shift specific plots.

Document the entire PX transaction — the initial offer letter, the developer's valuation report, the agreed price, and all completion statements — in your Property Passport UK. If questions about the valuation or the transaction arise when you later come to sell the new build, having the original PX paperwork available protects you.