Key facts: A mortgage in principle (also called an agreement or decision in principle) is a lender's written indication of what it would lend you, based on basic checks. It typically lasts 60–90 days, usually involves only a soft credit check, and is not a guarantee — the full application still follows.
What a mortgage in principle actually is
It's a statement from a lender — after basic income, outgoings and credit checks — saying "based on what you've told us, we'd expect to lend you around £X." Estate agents ask for one because it separates serious buyers from browsers; some won't put offers forward without it. It commits neither you nor the lender: you can still apply elsewhere, and the lender can still decline the full application if the detail doesn't match.
Does it affect your credit score?
Most lenders now use a soft search for an agreement in principle, which is invisible to other lenders and harmless to your score. A minority still run hard searches — worth checking before you proceed, especially if you plan to shop around. What genuinely damages files is scattergun applications: several hard searches in a short window reads as risk.
How long it lasts — and timing it right
Validity is typically 60–90 days depending on the lender, and refreshing an expired one is quick. The right time to get one is when you start viewing seriously — early enough to move fast on the right property, late enough that it doesn't expire mid-search. If your circumstances change (new job, new car loan, larger deposit), get it redone: an offer based on stale numbers helps nobody.
From principle to full offer
The full application verifies everything the principle assumed: payslips or accounts, bank statements, the property itself (valuation), and a hard credit check. This is where cases fall over when the principle was based on optimistic inputs — one reason to get the principle through a broker who has sanity-checked your figures against real lender criteria first, particularly if you're self-employed or have credit history issues.
Getting one the smart way
A broker can obtain a decision in principle from a lender actually likely to approve your full application — not just the first name on a comparison site — usually within a day. Get matched with a mortgage broker through Nesto — free, no obligation.
Frequently asked questions
Is a mortgage in principle a guarantee?
No. It's an indication based on basic checks. The full application — with documents, valuation and a hard search — can still be declined if the details differ.
Do I need one before viewing houses?
Not to view — but you'll want one before offering. Many estate agents won't submit an offer without it.
Does getting one hurt my credit score?
Usually not — most lenders use a soft search. Check before proceeding, as a minority still run hard checks.
How quickly can I get one?
Often the same day — sometimes within the hour through a broker with your documents ready.