A lot of buyers treat a pre-approval letter like a finish line. They get the letter, make an offer, and assume the money is locked in. It is not. A pre-approval is the lender saying that based on what they have seen so far, you look like a solid borrower. Between that letter and the closing table, the lender keeps watching, and your loan can still collapse if the picture changes. Knowing what can go wrong is the difference between a smooth closing and losing the house along with your earnest money.
The most common way buyers sink their own loan is by making a big purchase before closing. The new couch, the financed furniture set, the car they have been wanting, all of it changes the numbers the lender approved you on. Lenders pull your credit again right before closing, and new debt or a fresh hard inquiry can push your ratios out of range. Even buying appliances on a store card can do it. The rule is plain. From the day you apply until the day you sign, you make no new purchases on credit, and you open no new accounts.
Changing jobs is the next big one, and it surprises people because a new job often feels like good news. Lenders want stability, and they verify your employment again days before closing. If you switch employers, go from salaried to self employed, or move to commission based pay, you have changed the income they approved. Even a promotion can cause a delay if the pay structure is different. If a job change is unavoidable, tell your loan officer immediately so they can work with it instead of finding out at the worst possible moment. Silence is what turns a manageable change into a denied loan.
Money movement raises flags too. Lenders need to source every dollar going toward your down payment and closing costs. A large deposit that appears out of nowhere looks like an undisclosed loan to them, even when it is a gift from family. Moving cash between accounts without a clear paper trail creates the same problem. If someone is gifting you money, document it properly with a gift letter and keep the transfer clean and traceable. Do not move large sums around in the weeks before closing unless you can explain and prove where every amount came from.
The home itself can also break the deal even when your finances are perfect. The lender orders an appraisal, and if the house appraises below the agreed price, they will only lend against the lower value. That leaves you to cover the gap in cash or renegotiate, and not every deal survives it. The title search can turn up liens or ownership issues that have to be cleared first. These are not your fault, but they are still your problem, which is why a financing contingency and a clear timeline in your contract matter so much. Those protections exist to give you a way out without losing your deposit.
There are quieter risks worth watching as well. If interest rates jump before you lock your rate, your monthly payment can rise enough to push you out of qualification, so ask your lender when and how to lock. Co signing a loan for someone else adds debt to your profile even though you are not the one paying it. Letting a credit card balance creep up changes your utilization and your score. None of these feel connected to your mortgage in the moment, but the lender sees all of it when they take that final look at your file.
Protecting your approval comes down to a simple posture. Treat the weeks before closing as a freeze. No new debt, no job changes, no unexplained money, no surprises. Keep paying every existing bill on time, since a single late payment can drop your score at exactly the wrong moment. When anything in your financial life shifts, call your loan officer first instead of guessing. They would much rather hear about a change early than discover it during the final review.
A pre-approval gets you to the table, but the deal is not done until the loan funds and the keys are in your hand. The buyers who close without drama are the ones who understood that the lender never stopped watching. Keep your file boring and consistent from application to signing, and you remove almost every reason a loan falls apart. The house is worth a few weeks of discipline. Guard the approval the same way you fought to earn it.
