Mortgage in Principle FAQ
General information only. This is not financial advice.
Last reviewed: 2026-06-06
What is a mortgage in principle?
A mortgage in principle (MIP) is a conditional indication from a lender that they would be willing to lend a specified amount, based on an initial assessment of your income and credit profile. It is also called an Agreement in Principle (AIP) or Decision in Principle (DIP) — these terms are used interchangeably and refer to the same thing. A mortgage in principle is not a formal mortgage offer and does not constitute a binding commitment to lend. The lender will carry out a full underwriting assessment — including a full credit check, income verification, and property valuation — before issuing a formal mortgage offer. Estate agents frequently ask buyers to have a mortgage in principle before accepting an offer on a property, as it demonstrates that the buyer has had a preliminary affordability check.
Does getting a mortgage in principle affect my credit score?
It depends on whether the lender runs a soft or hard credit search. A soft credit search does not leave a visible footprint on your credit file and cannot be seen by other lenders — it will not affect your credit score. Most lenders now use soft searches for mortgage in principle applications. A hard credit search does leave a visible footprint and is recorded on your credit file. Multiple hard searches in a short period can reduce your credit score and may concern other lenders. If you are applying to multiple lenders for a mortgage in principle, confirm in advance whether each application involves a soft or hard search. Your broker can help you identify which lenders use soft searches at the AIP stage, reducing the risk of unnecessary credit file impact.
How long does a mortgage in principle last?
Most mortgage in principle certificates are valid for 60–90 days. After that period, you will need to refresh the application — either with the same lender (which may involve a new credit check) or with a new lender. If your financial circumstances change materially during the validity period — a new credit commitment, a change in employment, a change in income — you should inform the lender, as these changes may affect whether the initial indication still holds. A refreshed MIP is standard practice if your property search takes longer than anticipated. Your broker can advise on the best timing for applying for or refreshing a mortgage in principle in relation to your active property search.
Can I get a mortgage in principle if I am self-employed?
Yes. Lenders will issue a mortgage in principle for self-employed applicants, though the assessment at the AIP stage uses the income figures you declare, and full income verification (accounts, SA302s, tax year overviews) happens at the full application stage. For self-employed borrowers, it is particularly important that the income declared at AIP stage accurately reflects what can be evidenced at full application. If the income you declare at AIP stage cannot be verified at full application — for example, if your accounts show lower net profit than anticipated, or the lender does not accept the income type you have described — the full application may be declined even after an MIP was issued. A broker who specialises in self-employed and complex income mortgages can identify which lenders are most likely to confirm their MIP at full application stage for your specific income profile.
Will an estate agent accept my offer without a mortgage in principle?
Most estate agents will ask for evidence of a mortgage in principle before presenting your offer to the vendor. This is not a legal requirement, but it is standard practice because it provides evidence that you have had a preliminary affordability assessment and are a credible buyer. Without an MIP, some agents will still present offers from buyers who demonstrate other evidence of seriousness (for example, buyers who are chain-free, cash-ready to proceed, or who have an experienced broker providing a letter of confirmation). However, in a competitive market, not having an MIP can put you at a disadvantage. Obtaining an MIP before making an offer is straightforward and takes 20–30 minutes with a broker or directly with a lender online.
What is the difference between a mortgage in principle and a full mortgage offer?
A mortgage in principle is a preliminary indication based on limited information — typically your self-declared income, a soft credit check, and an approximate property value. It does not involve property valuation, full income verification, or detailed underwriting. A full mortgage offer is issued after the lender has verified all documentation (payslips or accounts, bank statements, ID), conducted a valuation of the specific property, and completed full underwriting against their lending criteria. A full mortgage offer is a binding commitment to lend on the specified property, subject to the terms stated. Between MIP and offer, a number of things can change the outcome: the valuation may come in below the purchase price, income documents may not support the amount declared at MIP stage, or the property may have structural or legal issues that affect its suitability as security.
Risk warning
Your home may be repossessed if you do not keep up repayments on your mortgage. A mortgage in principle is not a guarantee of a mortgage offer — full underwriting and valuation are required before any offer is binding.
Explore further