How Long Does a Mortgage in Principle Last?

You start looking at houses, the agent smiles and says, “Great, do you have a mortgage in principle?”

If your brain goes straight to panic, you’re not alone. It’s a really common step in the buying process, but most people only learn what it really means when they’re already in the thick of things.

Let’s break down what a mortgage in principle is, how long it lasts, how reliable it really is and what it means for your move if things change or fall through.

What is a mortgage in principle?

First things first, what is a mortgage in principle in plain English?

As MoneyHelper puts it, a mortgage in principle is “a written estimate of how much a mortgage provider is willing to lend you based on a quick check of your income and – in some cases – your credit file.” You’ll also hear it called an agreement in principle, a decision in principle or a mortgage promise. They all mean broadly the same thing.

It’s a conditional offer that gives you an idea of your budget, but it’s not a full mortgage offer and it’s not guaranteed. You only get a binding offer after the lender has looked closely at your documents, done full credit checks and valued the property.

How long will a mortgage in principle last?

Most UK lenders set a time limit, 30 to 90 days being the normal range. If yours expires before you’ve found a place, you can usually apply again, although the lender will look at your updated situation when you do.

Some lenders will go longer than 90 days, but 30-90 is the usual range. If you’re looking for a long-term offer, it might be worth picking your lenders accordingly, though as we’ll get into later, you can reapply if the first offer expires while you’re still looking.

If your house hunt slows down, make a note in your calendar a couple of weeks before it runs out so you’re not caught on the hop.

How reliable is a mortgage in principle in real life?

A mortgage in principle feels like a big green tick, but how reliable is a mortgage in principle when push comes to shove?

The honest answer is this: it’s helpful and it carries weight with estate agents, but it isn’t a promise carved in stone. It’s only an indication, not a guarantee.

A lender can still change its mind when it does full checks. For example, things can shift if:

• Your income goes up or down
• Your spending or other debts change
• Your credit report shows issues that were not obvious at the early stage
• The property valuation comes back lower than expected

So treat it like a strong maybe, not a definite yes. It’s there to guide you and show sellers you’re serious, not to lock the lender in before they’ve seen the full picture.

How to get a mortgage in principle, step by step

If you’re wondering how to get a mortgage in principle, we’ve got good news: the process is usually fairly quick.

You can often apply online with a bank, building society or via a broker. The form usually takes around 15 minutes if you’ve got your details to hand, and many lenders give you a decision almost instantly.

You’ll normally be asked for:

• Basic personal details
• Your income and employment situation
• Regular outgoings and debts
• An idea of your deposit

Many lenders use a soft credit check at this stage, which doesn’t leave a mark on your credit file, though some may still do a hard check. It’s always worth checking which type they use before you apply, especially if you’re shopping around.

Once it’s approved, you’ll usually get a document or email confirming the amount and the expiry date. You can show this to estate agents when you book viewings or make offers.

What if your mortgage in principle expires or changes?

Life happens. Your ideal property might not appear in time, or your circumstances might change. So, what if your mortgage in principle expires before you’ve found a home?

In most cases, you can simply apply again. The lender will ask for refreshed information and may run another credit check. Because they’re looking at your up-to-date situation, the amount they’re willing to lend can go up, down or stay the same.

If your income has dropped, your debts have risen or interest rates have moved a lot, your new figure might be lower. That can be unsettling if you’ve already set your heart on a certain price range, but it’s better to know now than to overstretch and struggle later.

If your mortgage in principle changes while you’re mid purchase, your broker or lender is your first call. You might be able to tweak the deposit, look at different products or choose a cheaper property. Citizens Advice also has clear guidance on how mortgages work and what happens if you’re struggling with payments, which is helpful background if you’re feeling wobbly about affordability.

When a shaky mortgage in principle puts your move at risk

A mortgage in principle isn’t just about you though. If you’re selling as well as buying, your buyer’s mortgage in principle matters too.

Sales can fall through if a buyer’s agreement in principle expires, their circumstances change or the full mortgage offer is refused. That can leave you with a broken chain, extra costs and a lot of stress. 

If your sale has collapsed because a buyer’s mortgage has fallen apart, you’ve got a few options. You can re-list and start again on the open market, but that takes time and there’s no guarantee a new buyer’s mortgage will be any smoother.

One alternative is to sell to a cash house buyer so you can move on without worrying about someone else’s mortgage in principle. That’s where we can help.

You deserve certainty on your next move

Buying or selling with a mortgage in the mix is a lot to juggle. Understanding how long a mortgage in principle lasts and how reliable it really is should make the whole thing feel a bit less mysterious and a bit more manageable.

If your mortgage has fallen through or you’ve simply had enough of waiting on chains and fragile agreements in principle, we’re here to offer a different route. At Sell House Fast we buy houses for cash across the UK, and we’re set up to complete in a matter of days when you need us to.

Our team follows The Property Ombudsman’s code of conduct, so you’ve got extra reassurance on fairness and standards throughout the process.

Here’s what you can expect if you decide to sell with us:

• A free, no obligation cash offer based on real market data
• A fast, flexible completion that often takes just a matter of days (or whenever suits you)
• No fees to pay and no repairs needed before you sell
• We buy any house, flat or bungalow in any condition across the UK

If you’re ready for more certainty and less stress around your move, you can get the ball rolling in minutes. Pop your postcode into our form, get your free cash offer and see how selling to Sell House Fast could help you.