Mortgage in principle: what it is and why agents want one
A mortgage in principle is an early sign from a lender of how much you may be able to borrow, based on an initial check of your finances. It
3 min read · Updated 8 August 2026 · By Dwellmark Editorial
A mortgage in principle, often shortened to AIP, is an early sign from a lender of how much you may be able to borrow. It can help you move faster when you start viewing homes, but it is not the same as a formal mortgage offer. Below: what an AIP is, whether it is usually free, what kind of credit search it involves, and why estate agents often ask to see one. Mortgages are regulated by the Financial Conduct Authority; this guide is general information, not financial advice.
Definition of Mortgage in Principle
A mortgage in principle, also called an agreement in principle or decision in principle, is a lender’s written sign of how much it would lend you based on an initial check of your finances. It is not a mortgage offer. Before making a formal offer, the lender still carries out a full affordability assessment and valuation, and the formal offer is the stage described here as legally binding on the lender.
Cost of Obtaining a Mortgage in Principle
The verified material says an AIP is usually free and can take minutes to get. It also lists a mortgage in principle as achievable the same day in a straightforward purchase, but that timing is specifically marked unverified in the source material.
Soft vs Hard Credit Searches
The material provided says an AIP usually involves a soft credit search that does not affect your credit score. However, there are no verified facts here about hard credit searches in this context, so no comparison can be made from the supplied evidence alone.
Duration of a Mortgage in Principle
An AIP is time-limited: the lender sets the validity period, and the expiry date is stated on the AIP itself. Validity is set by each lender, so the only number that matters is the one on your own document. If it lapses before you complete, get a fresh one: the check is quick, and a renewed AIP does exactly the same job with an updated date.
Importance of Mortgage in Principle for Agents
The material says estate agents and sellers normally expect buyers to have an AIP before accepting an offer, because it shows the buyer can realistically afford the property. In practice, that makes it useful proof at the offer stage, even though it is still only an initial indication rather than a full mortgage offer.
Key facts
| Fact | Status |
|---|---|
| A mortgage in principle (AIP), also called an agreement in principle or decision in principle, is a lender written indication of how much it would lend you, based on an initial check of your finances. | verified-primary |
| An AIP is usually free, takes minutes to obtain, and involves a soft credit search that does not affect your credit score. | verified-primary |
| Estate agents and sellers normally expect buyers to have an AIP before accepting an offer, because it shows the buyer can realistically afford the property. | verified-primary |
| An AIP is not a mortgage offer: the lender carries out a full affordability assessment and valuation before making a formal offer, which is legally binding on the lender. | verified-primary |
| A mortgage in principle is time-limited: the lender sets the validity period, the expiry date is on the AIP document, and you can get a fresh one if it lapses before completion. | verified-primary |
| Realistic timings for a straightforward purchase: mortgage in principle the same day. | unverified |
Source: HM Land Registry - buying your first home — see source
Source: FCA - mortgages consumer guidance — Guidance checked August 2026
Source: FCA - mortgages consumer guidance — Guidance checked August 2026
Source: Citizens Advice - buying a home — Guidance checked August 2026
Information and review status
This article provides general information only and is not professional advice. It was last reviewed and updated on 2026-08-08 using the sources cited in this article. Unless expressly stated otherwise, it has not been independently reviewed by a suitably qualified external professional. Laws, regulations, guidance, prices and market conditions can change, so you should verify information relevant to your circumstances before relying on it.Generated from dossier mortgage-in-principle. Review before publishing.
Sources
- HM Land Registry - buying your first home - see source
- FCA - mortgages consumer guidance - Guidance checked August 2026
- FCA - mortgages consumer guidance - Guidance checked August 2026
- Citizens Advice - buying a home - Guidance checked August 2026
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