How long does a mortgage agreement in principle last?

Usually between 30 and 90 days, depending on the lender, with 90 days common at the big banks and building societies. If it expires before you have offered on a property, you can simply apply for a new one at no cost.

Does an agreement in principle guarantee a mortgage?

No. It is an indicative decision based on a quick check. When you apply for real, the lender verifies your income, runs the full affordability assessment and values the property, any of which can change the amount or decline the application.

Does a mortgage in principle affect my credit score?

It depends on the lender. Many use a soft credit check that leaves no visible mark, so your score is unaffected. Some run a hard check that is recorded, and several hard checks in a short period can lower your score, so ask which type each lender uses.

Do I need an agreement in principle to view houses?

Not to view, but it helps when you offer. Estate agents and sellers often want to see an AIP as proof you can afford the property, and it also gives you a realistic budget before you start looking seriously.

Guide · 3 minute read · Updated 10 Jul 2026

Mortgage in principle: what it is and how long it lasts

An agreement in principle is a lender's early, indicative yes: based on a quick check of your income and credit file, it says roughly how much it would be willing to lend. It usually lasts 30 to 90 days, it is not a guaranteed offer, and estate agents will often want to see one before they take your offer seriously.

What it actually is

An agreement in principle, also called a decision in principle, AIP or DIP, is a statement from a lender that it would in principle lend you a given amount, subject to full checks. The lender runs your basic details, income and a credit search, then produces a figure and a document you can show sellers and agents.

It matters because it does two jobs. It gives you a realistic budget before you start viewing, and it signals to sellers that you are a credible buyer rather than someone guessing. In a competitive market, an offer backed by an AIP tends to be taken more seriously than one without.

How long it lasts

Most agreements in principle are valid for 30 to 90 days, with 90 days being common at the larger lenders. If yours expires before you have found and offered on a place, you simply apply for a new one; there is no penalty for letting it lapse and starting again.

Because it is time-limited, do not rush to get one the moment you start idly browsing. Get it when you are genuinely ready to view and offer, so that its clock is running while you are actively house-hunting rather than expiring on the shelf.

It is not a mortgage offer

This is the part people misread. An agreement in principle is not a binding commitment from the lender, and it is not the same as a formal mortgage offer. When you find a property and apply properly, the lender underwrites you fully: it verifies your income with payslips or accounts, checks the affordability sums against your outgoings, and values the property. Any of those can change the number, or turn a yes into a no.

So treat the AIP figure as a well-informed estimate, not money in the bank. The affordability assessment at full application is the real test, and it is worth sense-checking your own numbers with the mortgage affordability calculator so the formal decision holds no surprises.

The effect on your credit file

Whether an AIP touches your credit file depends on the lender. Many run a soft credit check, which only you can see and which leaves no mark, so it does not affect your score. Some, though, run a hard check, which is recorded and visible to other lenders.

One hard check is nothing to worry about. The risk is doing several in a short space of time, for instance getting an AIP from four different lenders in a fortnight, because a cluster of hard searches can dent your score just as you want it at its best. If you are shopping around, ask each lender which type of check it uses, or work through a broker who can steer you to soft-search lenders first.

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Common questions

How long does a mortgage agreement in principle last?: Usually between 30 and 90 days, depending on the lender, with 90 days common at the big banks and building societies. If it expires before you have offered on a property, you can simply apply for a new one at no cost.
Does an agreement in principle guarantee a mortgage?: No. It is an indicative decision based on a quick check. When you apply for real, the lender verifies your income, runs the full affordability assessment and values the property, any of which can change the amount or decline the application.
Does a mortgage in principle affect my credit score?: It depends on the lender. Many use a soft credit check that leaves no visible mark, so your score is unaffected. Some run a hard check that is recorded, and several hard checks in a short period can lower your score, so ask which type each lender uses.
Do I need an agreement in principle to view houses?: Not to view, but it helps when you offer. Estate agents and sellers often want to see an AIP as proof you can afford the property, and it also gives you a realistic budget before you start looking seriously.

Guidance and education, not regulated financial advice.