Getting approved isn't a one-time photo. Your lender takes a snapshot when you apply — then takes another one right before closing. If the second picture doesn't match the first, the deal can wobble or fall apart. So the whole stretch between application and keys comes down to one rule: don't rock the boat.
Don't take on new debt
A new car loan, a financed couch, a new credit card — each one adds a monthly payment that raises your DTI, and each can trigger a hard inquiry. Lenders re-pull credit before closing more often than people expect. A purchase that felt completely unrelated to your mortgage can be the exact thing that pushes your ratios out of bounds at the worst possible moment.
Don't make large purchases or drain your savings
Lenders want to see reserves and a stable down payment. Wiping out your accounts on furniture or a trip — even after you've been approved — can undercut the cash you're supposed to bring to closing, and large unexplained swings invite questions you'll have to answer.
Don't change jobs (if you can help it)
Income stability is load-bearing. Switching employers mid-process — especially into a different industry, into self-employment, or onto a commission structure — can force the lender to re-verify everything and, in some cases, restart the clock on how your income is calculated. If a job change is unavoidable, tell your loan officer before you do it, not after.
Don't shuffle money around
Large, undocumented deposits are a red flag. Moving cash between accounts, accepting an unexplained transfer, or depositing a wad of cash can each trigger a request for a paper trail you may not be able to produce. Keep your money boring and traceable until you've closed.
Don't let anything go late
A single missed or late payment on any account during the process can ding your score and rattle the file. Put everything on autopay and leave it alone for now.
The one "do"
Keep your financial life intentionally dull, and ask before any big move. A two-minute call to your loan officer before you open a card, change jobs, or move money can save the entire transaction. The borrowers who close without drama are simply the ones who treated the in-process window as a hold-still zone.
What triggers an underwriting problem varies by lender and loan program — when in doubt, clear any major financial move with your loan officer first.