Mortgage in principle: how long does it last?

A mortgage in principle (often shortened to MIP, and sometimes called a decision in principle (DiP) or agreement in principle (AiP)) is intended to give you an early steer on how much a lender may be willing to lend.

Because it’s based on the information provided at the time of assessment, it’s best thought of as a time-limited snapshot rather than a permanent commitment.

How long is a mortgage in principle valid for?

There isn’t one single expiry date that applies to every lender. Each lender sets its own validity period, and the exact timeframe will be shown on your mortgage in principle document.

In practice, many mortgage in principle decisions are valid for around 30 to 90 days (often described as roughly three months), but this can be shorter or longer depending on:

• the lender’s internal process
• the type of mortgage being considered
• how complete the information was at the time of assessment

Always check the “valid until” date on your decision—this is the point you should plan around.

Why the validity period can be different

Even where two borrowers apply around the same time, the validity window can vary because the lender may treat the application differently based on the details provided.

Common reasons include:

• Lender-specific documentation requirements (some lenders may expect more information upfront)
• Mortgage type and assumptions (for example, the way affordability is assessed for different products)
• Expected timeline to the next stage (the lender may set a shorter window if they anticipate a quicker progression)

Market conditions and lending criteria can also shift over time, which is another reason the validity date matters.

What can cause a mortgage in principle to be updated?

A mortgage in principle is based on the facts supplied at the time it was issued. If those facts change, the lender may need to reassess before you move further.

Things that can trigger an update (or require a refresh) include:

• Changes to income or employment
• Changes to outgoings (for example, new commitments or reduced income)
• Changes to credit profile
• Alterations to the deposit
• Delays in the purchase that push you beyond the validity window

In other words, even if your decision hasn’t technically expired, significant changes to your circumstances can affect what happens next.

What happens if your mortgage in principle expires?

If your mortgage in principle runs out before you reach exchange, you may need to obtain an updated decision.

The refresh process varies by lender, but it typically involves confirming that the information used previously is still accurate—particularly around affordability and the details that support the assessment.

If your circumstances have changed since the original decision, the updated result may differ, including the amount the lender is willing to consider.

Timing your mortgage in principle during a property search

A mortgage in principle can be issued early, but applying too far in advance can increase the chance you’ll need an update.

Practical timing points include:

• Aim to have it in place before making offers, so you can move quickly when you find the right property
• Avoid applying too early if your search could take longer than the validity window
• Factor in delays such as chain complexity, slower conveyancing, or extended searches

If your purchase timeline is uncertain, it can help to keep the mortgage process aligned with where you are in the buying journey.

Mortgage in principle vs mortgage offer (why expiry isn’t the whole story)

A mortgage in principle helps you understand the likely direction of travel, but it’s not the same as a formal mortgage offer.

Between the two stages, lenders typically carry out further checks, including:

• more detailed affordability assessment
• property-related checks and valuation
• confirmation of the final loan amount and terms

So even if your mortgage in principle remains valid, the full application still needs to progress successfully to reach a mortgage offer.

Key takeaways

• Mortgage in principle validity depends on the lender. There’s no universal expiry date.
• Many decisions are valid for around 30 to 90 days, but you should rely on the “valid until” date on your document.
• Validity can be affected by changes in your circumstances and delays in the purchase.
• If it expires, you may need an updated decision before you can progress.

Mortgage in principle terminology you may see

You might come across different labels for the same concept:

• Mortgage in Principle (MiP)
• Agreement in Principle (AiP)
• Decision in Principle (DiP)

Regardless of the name, the key point is the same: it’s provisional and time-limited.