What an AIP actually is
An Agreement in Principle (also called a Decision in Principle or Mortgage in Principle) is a lender's estimate of how much they'd be willing to lend you, based on some basic information and a quick credit check. It's not a full mortgage offer, and it isn't guaranteed — the full application later involves a much deeper look at your finances — but it's a genuinely useful first step that gives you a realistic budget to work with.
Soft search vs hard search
The type of credit search a lender runs for an AIP matters, since it affects whether it leaves any visible trace on your credit file.
We'll always tell you which type of search applies before going ahead with any particular lender, so there are no surprises on your credit file.
Soft search
Used by most lenders for an AIP. Doesn't leave a visible mark on your credit file and doesn't affect your credit score — only you can see it.
Hard search
Used by a handful of lenders even at AIP stage. Leaves a visible record other lenders can see, and multiple hard searches in a short period can affect your score.
Why estate agents ask for one
Estate agents deal with a lot of buyers who aren't actually in a position to proceed. An AIP is a quick way for them to see you're a serious, credit-checked buyer before they'll put an offer forward to a seller — in a competitive market, not having one ready can genuinely cost you a property to another buyer who does.
How long it lasts
AIPs are typically valid for 60–90 days, depending on the lender. If your house search takes longer than that, it's usually simple enough to renew — just something to keep in mind if you're taking your time finding the right place, rather than assuming your original AIP will still be valid months later.
What can change afterwards
An AIP is based on limited information, so the full application — which comes later, once you have an accepted offer — involves a much deeper look at your finances, plus (usually) a hard credit search and a full underwriting review. Significant changes to your circumstances between the two — new debts, a change in income, a new job — can affect the final outcome, which is why we always advise keeping things as stable as possible during this window.
Getting the most accurate AIP
The more accurate the information you give at AIP stage, the less risk of an unpleasant surprise at full application. It's tempting to round income up or overlook a credit commitment, but an AIP based on optimistic figures can set expectations that don't survive the full underwriting review later — far better to start with an honest, accurate picture from the outset.
