TL;DR: A UK mortgage in principle (also called a Decision in Principle or Agreement in Principle) is an indicative statement from a lender that, based on the information provided, the lender would lend a specified amount subject to a full application and valuation. It is not legally binding and the lender can withdraw or reduce it. Reliability is moderate: a mortgage in principle from a lender that has carried out a full credit search and based the figure on the applicant's actual income data is usually a fair indication of what the lender will offer. A mortgage in principle from a soft-search-only or income-self-declared process is much less reliable. Common reasons applications fail after a positive mortgage in principle include changes in the applicant's circumstances, the property failing the valuation or being unsuitable security, undisclosed adverse credit, the lender's criteria changing, and lender errors in the original assessment. Most agents now expect a mortgage in principle to be in place before they accept an offer.
Last reviewed May 2026
"Mortgage in principle" is the phrase used to describe a lender's indicative pre-approval of a mortgage application. The phrase covers a range of products. Some are produced after a full credit search and detailed income assessment, others after a soft credit check and self-declared income. The reliability of the mortgage in principle as a predictor of the eventual mortgage offer varies accordingly.
This guide sets out what a mortgage in principle actually is, the differences between the various forms used by UK lenders, the practical reliability based on FCA and industry data, what can change between mortgage in principle and full offer, and how a buyer should use it.
What a mortgage in principle actually is
A mortgage in principle is an indicative statement from a lender about how much it would in principle lend to a specific applicant, based on the information provided. It is not a legally binding offer of a mortgage. The lender can withdraw or reduce the indicative amount before a full mortgage offer is issued. The mortgage in principle is normally valid for a defined period (commonly 30 to 90 days), after which it expires and the applicant has to re-apply.
The mortgage in principle is most commonly used by buyers who want to make an informed offer on a property and by estate agents who want assurance that a buyer can fund their offer. Most agents now require a mortgage in principle from a buyer before formally putting their offer to the seller. Mortgage in principle is not the same as a "mortgage offer" or "binding offer"; that is the formal document the lender issues after a full application, credit and affordability assessment, and valuation.
Hard search versus soft search
The single biggest variable in mortgage in principle reliability is whether the lender carried out a "hard" or "soft" credit search. A hard credit search produces a footprint on the applicant's credit file and is the same kind of search the lender will do on a full application; the result is therefore a fair indication of the lender's view of the applicant's credit profile. A soft credit search is invisible to other lenders, has no effect on the applicant's credit profile, and provides less depth of information to the assessing lender.
Most large UK lenders now use soft search for the initial mortgage in principle to avoid leaving multiple credit footprints on prospective buyers. The result is a faster, smoother applicant experience but a less rigorous pre-assessment. A "passed" mortgage in principle from a soft search can later fail when the full application triggers a hard search and reveals adverse credit, additional debt, or affordability issues that were not visible in the soft check.
The reliability of the income assessment
Some mortgage in principle processes ask the applicant to enter their income and outgoings figures, which the lender's affordability calculator processes without independent verification. Others integrate with Open Banking or other data sources to verify income directly. The latter produces a more reliable estimate.
For an employee on PAYE, the lender will eventually verify income by reviewing payslips and bank statements. If the applicant's stated income is accurate, the eventual underwriting normally aligns with the mortgage in principle. For self-employed applicants, the lender will eventually require SA302s, full accounts, or accountant certifications; the eventual decision can diverge significantly from the mortgage in principle if the lender interprets the accounts differently. Contractor and bonus income are particularly likely to produce a difference between the mortgage in principle and the formal offer.
What can change between mortgage in principle and full offer
Several factors can cause the formal mortgage offer to differ from the mortgage in principle: changes in the applicant's circumstances (job change, new debt taken on, separation, child arrival), undisclosed or under-disclosed information that emerges in the full application, additional credit checks revealing adverse credit, the property failing the valuation or being unsuitable security, lender criteria changes between the mortgage in principle date and the application, and lender errors in the original mortgage in principle assessment.
The property itself is a frequent source of decline. A property that the lender's valuer believes is overvalued, has structural defects, is non-standard construction, has remaining lease too short for the loan term, has cladding issues without an EWS1, sits on land with environmental risk, or is otherwise unsuitable can result in a reduced loan amount or a decline. The lender's underwriting also looks at the local market evidence; if comparable sales do not support the agreed price, the loan may be capped at the lower valuation.
Industry data on conversion rates
UK Finance and the FCA periodically publish data on mortgage application progression through the funnel. While the published series do not isolate "mortgage in principle to offer" specifically, lender experience and broker commentary suggest that a meaningful percentage of applications that pass mortgage in principle do not progress to a full offer at the originally-quoted amount. Reasons split roughly between income or affordability re-evaluation, property-specific issues, and applicant withdrawal.
For straightforward cases (employed applicant on PAYE, standard property, no chain issues), the mortgage in principle typically converts to a full offer at the same or similar amount. For complex cases (self-employed, contractor income, multiple sources, properties with characteristics, large loan-to-value), the eventual offer can diverge materially. A broker with experience of the specific lender can usually predict which mortgage in principle approvals are likely to convert.
How long a mortgage in principle is valid
Lenders set their own validity period. The common range is 30 to 90 days, with 60 days being typical. After expiry, the applicant has to re-apply for a new mortgage in principle. Each new application has its own credit and affordability checks; if applicant circumstances have changed in the meantime, the new mortgage in principle may produce a different result.
For a buyer who has had an offer accepted but is still some way from exchange, the mortgage in principle may expire before the full application is submitted. Most lenders will refresh the assessment if asked; some will simply require a full application. The buyer should monitor the validity and not let it lapse silently.
The credit file footprint question
If the mortgage in principle uses a hard search, the search appears on the applicant's credit file and other lenders can see it. Multiple mortgage in principle hard searches in a short period can negatively affect the credit score and signal to other lenders that the applicant is shopping around. Most large UK lenders have switched to soft search for the initial mortgage in principle to address this.
The full mortgage application later in the process always uses a hard search regardless of how the mortgage in principle was conducted. A single hard search at full application is not normally a problem; a credit profile with many recent hard searches can be. Brokers usually advise applicants to limit the number of mortgage in principle applications they trigger to those they actually want to compare on rate or eligibility.
How to use a mortgage in principle properly
Use the mortgage in principle as a planning tool, not a guarantee. The most useful information it provides is: the lender thinks the applicant could borrow approximately this amount; the lender's initial credit-and-affordability check did not reveal a fundamental problem; the lender is willing to progress to a full application. It does not provide a binding loan offer, a guarantee on rate, or certainty that the eventual offer will be at the same amount.
For an offer on a property, the mortgage in principle is normally enough to put the offer to the agent. For the formal property purchase to complete, a full mortgage offer is needed. The buyer should submit the full application quickly after the offer is accepted, with all supporting documents ready, so the formal offer is in place before exchange. A broker often coordinates this and can identify in advance lenders where the mortgage in principle is more or less likely to convert into a full offer.
How we verified this
The framework set out here is based on the FCA's MCOB rules on mortgage conduct (particularly the disclosure and pre-application standards), UK Finance market commentary on mortgage application progression, the published criteria from the major UK lenders on their mortgage in principle processes, and the FCA's product disclosure and credit reference agency guidance. Validity periods and the choice between hard and soft search are lender-specific and the specific terms should be checked with the lender or broker. No regulatory or product figure has been fabricated.
Disclaimer: This article is general information about UK mortgages in principle. It is not personal financial advice and it does not recommend any specific lender. The reliability and the terms of any specific mortgage in principle depend on the lender and the applicant's circumstances. Anyone planning a property purchase should consider speaking to an FCA-authorised mortgage adviser.
Frequently asked questions
How reliable is a mortgage in principle?
Reliability is moderate and depends on the lender's process. A mortgage in principle from a lender that has carried out a full credit search and based the figure on the applicant's actual income data is usually a fair indication of what the lender will offer. A mortgage in principle from a soft-search-only or self-declared-income process is less reliable. The formal mortgage offer can still differ because of property-specific factors, criteria changes, or circumstances that emerge during the full application.
How long does a mortgage in principle last?
Validity varies by lender, with the common range 30 to 90 days. Sixty days is typical. After expiry, the applicant has to re-apply for a new mortgage in principle. If the applicant's circumstances have changed in the interim, the new mortgage in principle may produce a different result.
Can a mortgage in principle be refused at the full application stage?
Yes. A positive mortgage in principle is not a binding offer. The full application can result in a different decision because of further information revealed in the full credit check, additional documents required for income verification, property issues identified in the valuation, criteria changes by the lender, or applicant circumstances changing between the mortgage in principle date and the full application.
Does a mortgage in principle affect my credit score?
It depends on whether the lender uses a hard or soft credit search for the mortgage in principle. A hard search appears on the applicant's credit file and other lenders can see it; multiple hard searches in a short period can have a small negative effect on credit score. Most large UK lenders now use a soft search for the mortgage in principle stage, which has no effect on the credit file. The full mortgage application later in the process always uses a hard search.
How long does it take to get a mortgage in principle?
Online mortgage in principle applications from most major lenders return a decision within minutes or hours when the applicant's information is straightforward and the credit check returns cleanly. More complex cases (self-employed income, foreign income, adverse credit history) can take a few working days because manual underwriter input is required. A mortgage broker can often submit several applications and compare results within a working day.
