Mortgage in Principle Explained

What this means in practice

A mortgage in principle is a written statement issued by a mortgage lender that sets out how much it might be willing to lend to a specific borrower, based on a high-level review of the borrower's circumstances. The term mortgage in principle is interchangeable with agreement in principle, sometimes abbreviated to AIP, and decision in principle, abbreviated to DIP. The document is not a binding mortgage offer. It is a statement of indicative lending capacity issued at a stage when the lender has not yet conducted full underwriting or verified the borrower's documents.

For a first-time buyer in the UK, a mortgage in principle plays two main roles. The first is to give the buyer a working budget for the property search, by indicating the maximum loan a lender might be prepared to provide. The second is to demonstrate to estate agents and sellers that the buyer has a credible source of finance, which can make the difference between an offer being taken seriously and being passed over. Many estate agents will not progress an offer without seeing a mortgage in principle, particularly in competitive markets, and many now ask for proof of deposit alongside the AIP.

How it works

The mechanics of a mortgage in principle vary slightly between lenders, but the core process is consistent. The buyer provides details of personal circumstances, including age, residency status, income, employment, household composition, regular outgoings, existing credit commitments, and the size of the deposit they intend to use. The lender combines this information with a credit reference check and applies its lending criteria to issue an indicative maximum loan figure. Many lenders complete this online in minutes, with no human underwriter involved at the initial stage.

Soft and hard searches

The credit check at this stage is usually a soft search. A soft search is visible to the buyer on their credit file but is not visible to other lenders, so it does not affect the way subsequent lenders score the application. This means a buyer can obtain mortgage agreements in principle from more than one lender without damaging their credit profile. A small number of lenders use a hard search at the agreement in principle stage; a hard search is visible to other lenders and can have a minor impact on credit scores, particularly when several occur in a short period. Buyers can verify the search type by asking the lender or broker directly, or by reviewing their credit file at a credit reference agency such as Experian, Equifax, or TransUnion after the AIP has been issued.

The role of the broker

Many first-time buyers obtain their mortgage in principle through an FCA-authorised mortgage broker rather than directly from a lender. A broker can match the buyer's profile to lender criteria across the wider market, increasing the chance that the chosen lender will produce an offer at the full application stage. Brokers regulated under FCA Mortgage Conduct of Business rules must follow the same suitability standards as a lender's in-house adviser. A broker-issued AIP comes through an advised process under MCOB, with the broker accountable for the recommendation. A direct-to-lender AIP can be obtained through the lender's execution-only channel, where the buyer makes the product selection without advice. The FCA disclosure regime distinguishes between these channels and the buyer should be aware which they are using.

Eligibility and qualifying conditions

There is no formal eligibility test for obtaining a mortgage in principle beyond the lender's general residential mortgage criteria. Applicants typically need to be at least 18 years old, hold the right to reside and work in the UK or otherwise meet residency conditions, have a verifiable income, and have a credit history that is acceptable to the lender. The agreement in principle stage filters out applications that obviously do not meet the lender's criteria, but it does not verify any of the information provided.

Joint applicants both need to be assessed at the agreement in principle stage if they will be on the eventual mortgage. The lender will consider the combined income, the lower of the two credit scores, and the joint outgoings. Applicants on probation periods or with recent changes in employment may find some lenders willing to proceed with an agreement in principle while others decline at this stage, reflecting different risk appetites across the market.

Self-employed applicants generally face a more involved process, with lenders looking for at least one and preferably two or three years of trading history. An agreement in principle for a self-employed applicant indicates that the lender's basic criteria are met, but the full application will require detailed accounts, tax calculations, and tax year overviews from HMRC. The agreement in principle is therefore a weaker signal of likely full approval for self-employed buyers than for employees on stable salaries.

Key figures and thresholds

The validity period of a mortgage in principle is typically 30 to 90 days, depending on the lender. After that period, the agreement expires and the buyer may need to repeat the process if they have not yet had an offer accepted on a property. Some lenders allow an extension on request without a full reassessment, while others require a fresh application that may include a new credit search.

The maximum loan figure on a mortgage in principle reflects the lender's affordability assessment at that moment. It is generally bounded by the loan-to-income flow limit set by the Bank of England Financial Policy Committee, which restricts each lender so that no more than 15% of new mortgages can exceed 4.5 times borrower income. Within that constraint, lenders apply their own affordability models, considering committed outgoings, dependants, and stress assumptions about future interest rates. Although the Bank of England removed its mandatory affordability stress test in August 2022, FCA MCOB rules still require lenders to apply internal stress rates.

The loan-to-value ratio implied by an agreement in principle depends on the deposit the buyer indicates they will use. A buyer who later increases the deposit can move into a lower loan-to-value band, potentially accessing better products. A buyer whose deposit falls short of expectations at the full application stage may find their loan capped at a higher loan-to-value than indicated. These movements are normal and the agreement in principle is best understood as a guide rather than a guarantee.

What the AIP does not guarantee

An agreement in principle is not a full mortgage offer. The distinction matters because the AIP relies on self-declared information, a high-level credit check, and the lender's automated decisioning. A formal mortgage offer is issued only after the lender has completed full underwriting, verified the buyer's documents, run a hard credit search, and obtained a property valuation. Each of those stages can produce a different outcome from the AIP. The Mortgage Offer is the binding contract, subject to the conditions it specifies, while the AIP is only an indication. Lender criteria can change between the AIP and the application, particularly if there has been a meaningful market move or a policy update.

An AIP also does not address the property. The lender's valuation, instructed once a property has been identified, may produce a figure below the agreed purchase price. The valuation can also flag the property as unsuitable security, for example because of construction type, tenure, or proximity to a commercial use. The AIP, issued without reference to a property, cannot anticipate any of these factors.

How to apply and next steps

The practical application process for a mortgage in principle starts with assembling the necessary information: identity documents, address history typically going back three years, income details for all applicants, regular outgoings, and an indication of the deposit available. The buyer then completes the lender's online or in-person application, which usually takes between 15 and 30 minutes. Many lenders return a result within minutes, although some take longer if the application falls outside automated decisioning.

Once the agreement in principle is in hand, it can be shared with estate agents when making offers on properties. Agents increasingly expect to see proof of deposit alongside the AIP, often in the form of recent bank statements or a letter from a savings provider, on the basis that the AIP only confirms borrowing capacity and not the equity contribution. There is no obligation on the buyer to use the same lender at the full application stage; some buyers obtain an agreement in principle with one lender to support the property search and then switch to a different lender once a property is identified, often through a broker who searches the market.

When an offer is accepted, the next step is a full mortgage application. This involves a hard credit search, document verification, and a property valuation arranged by the lender. The lender's underwriters review the application in detail and issue either a formal mortgage offer or a decline. The full application typically takes two to six weeks to complete, depending on lender workload, property complexity, and the speed of the buyer's response to information requests.

Risks and downsides

The first risk to understand is that a mortgage in principle is not a binding offer. The lender can decline at the full application stage if information provided initially turns out to be inaccurate or if the underwriter takes a different view of the borrower's affordability, credit history, or the property's suitability as security. Buyers who treat an agreement in principle as a guarantee of finance may find themselves committing to a property purchase that the lender does not ultimately fund.

A second risk is the time-limited validity of the document. A buyer who obtains an agreement in principle and then takes six or nine months to find a suitable property may find the agreement has expired and that lender criteria have changed in the meantime. Interest rate movements, changes in employment, or new credit commitments can all alter the lender's assessment in a fresh application.

A third risk relates to multiple applications. Most lenders use soft searches at the agreement in principle stage, so running several soft AIPs across different lenders to compare positions is generally a low-risk activity for the credit file. The picture changes where lenders use hard searches: running three or four hard AIPs within a month can leave a visible pattern of credit-seeking behaviour that other lenders may interpret negatively under FCA Consumer Credit, or CONC, regulated scoring practices. Buyers planning to compare offers should confirm with each lender or broker that a soft search will be used before submitting the application, and check their credit file with a credit reference agency where there is any doubt. The Information Commissioner's Office sets out consumers' rights to challenge inaccurate credit data with the agencies under data protection law.

A fourth risk is misalignment between the agreement in principle and the property eventually purchased. An agreement in principle issued on the basis of one type of property may not translate cleanly to a different type. For example, ex-local-authority flats, properties of non-standard construction, or properties above commercial premises may face stricter lender criteria. Buyers should consider the property type when reviewing the lender's wider criteria, not just the agreement in principle headline figure.

Important disclaimer

This article is general information based on UK government, FCA, and Bank of England sources and does not constitute financial, legal, or tax advice. Mortgage availability, rates, lender criteria, and government schemes change; figures reflect the position at publication date. Readers facing a significant mortgage decision should consult an FCA-authorised mortgage adviser before acting.

Frequently asked questions

Is a mortgage in principle the same as a mortgage offer?

No. A mortgage in principle is an indicative statement of how much a lender might be willing to lend. A formal mortgage offer is the binding lender contract issued only after full underwriting, document verification, hard credit search, and a property valuation.

How long is a mortgage in principle valid?

Most agreements in principle are valid for 30 to 90 days. Some lenders allow an extension or refresh without a full reassessment, while others require a new application with a fresh credit search.

Does getting a mortgage in principle affect a credit score?

Most lenders use a soft search at this stage, which does not affect credit scores at other lenders. A small number use a hard search, which is visible and can have a minor effect, particularly with several in quick succession.

Can a buyer obtain more than one mortgage in principle?

Yes. Running several soft-search AIPs across different lenders is generally low risk for the credit file. Running multiple hard-search AIPs in a short period can leave a visible pattern, so the buyer should confirm the search type before applying at each lender.

Is a mortgage in principle required to make an offer on a property?

It is not legally required, but most UK estate agents and developers expect to see one before progressing an offer, frequently together with proof of deposit. A mortgage in principle signals that the buyer has credible financing in place.

What is the difference between an advised and execution-only AIP?

An AIP arranged through an FCA-authorised broker is usually advised under MCOB, with the broker accountable for the recommendation. A direct-to-lender AIP can be execution-only, with the buyer making the product choice without advice. The FCA disclosure regime distinguishes between these channels.

Can a mortgage in principle be declined at full application?

Yes. Underwriting reviews the documents and property in detail. Discrepancies, undisclosed credit, changes in employment, lender criteria changes, or property-specific issues can all result in a decline at full application.