What a Decision in Principle does and doesn’t guarantee you
One of the most common misunderstandings in the early stages of buying a property is what a Decision in Principle means. It goes by several names depending on the lender: Agreement in Principle, Mortgage in Principle, or sometimes simply an AIP or DIP. Whatever it is called, the document does the same thing: it tells you how much a lender may be willing to lend you based on an initial review of your circumstances. What it does not do is promise that the money will materialise when you need it. Understanding the gap between those two things before you start viewing properties is one of the most useful things any buyer can do.

What a Decision in Principle involves
The process of obtaining a Decision in Principle is straightforward. You provide a lender or mortgage broker with information about your income, your regular financial commitments, any debts you hold, and the deposit you have available. The lender reviews this information alongside a credit check and produces a written indication of the amount they may be prepared to lend.

In most cases, this credit check is a soft search. A soft credit check allows the lender to review a summary of your credit history without leaving a visible mark on your credit file that other lenders can see. It has no effect on your credit score and does not indicate to future lenders that you have been assessed for credit. Some lenders use a hard search instead, which does leave a visible footprint. It is worth asking which type of check a lender runs before you proceed, because multiple hard searches in a short period can have a modest negative effect on your credit profile.

Most lenders provide a Decision in Principle free of charge. It does not commit you to applying for a mortgage with that lender, and obtaining one from one lender does not prevent you from applying to others.

What the Decision in Principle is for
The immediate practical use of a Decision in Principle is to give you a realistic upper limit for your property search. Rather than estimating what you might be able to borrow from a calculator or a rule of thumb, you have an actual figure from an actual lender based on your specific financial position. That figure shapes the price range you search within and prevents the frustration of falling in love with a property that was always outside your realistic reach.

It also serves a commercial function in your dealings with sellers and agents. An offer from a buyer who can demonstrate they have a Decision in Principle in place carries more credibility than one from a buyer whose financial position is entirely unverified. Sellers weighing competing offers, or agents advising sellers on the strength of each offer, will factor in the perceived certainty of each buyer’s ability to proceed. A Decision in Principle does not make an offer binding or guaranteed, but it signals preparation and serious intent.

A Decision in Principle typically remains valid for between 30 and 90 days, depending on the lender. If it expires before you have agreed a purchase, you can usually obtain a new one.

What a Decision in Principle does not do
This is the part that catches buyers out, and it is worth being direct about it. A Decision in Principle is not a mortgage offer. It is not legally binding on the lender. It does not guarantee that the lender will provide you with a mortgage, that you will be able to borrow the full amount indicated, or that the eventual interest rate or product terms will be the same as anything discussed at the DIP stage.

The full mortgage application, which happens after an offer has been accepted on a specific property, involves a complete affordability assessment based on documented evidence of your income and outgoings, a full hard credit search, and a valuation of the property itself. Any of those stages can produce a different outcome from the initial DIP assessment.

The most common reasons a mortgage application does not proceed as expected after a Decision in Principle was issued include: a change in circumstances between the DIP and the application, such as a job change, a new debt, or a reduction in income; differences between the details given at DIP stage and the documents provided with the full application, or issues found in the lender’s more detailed checks; the property failing to meet the lender’s lending criteria due to construction type, lease length, or structural condition; or the formal property valuation coming in below the agreed purchase price.

None of these scenarios can be ruled out by holding a DIP. What a DIP can do is give you the most reliable starting point available, confirm the rough territory of your budget, and put you in a stronger position as a buyer before you begin the serious part of your search.

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