Your credit score affects whether you are approved and what rate you are offered. On a thirty-year loan, a difference of a fraction of a percent is real money — often tens of thousands over the life of the loan.
The score you see is not the score they use
This catches people out. The number in your banking app or a free credit site is usually an educational score built on a different model. Mortgage lenders use specific scoring versions, and they pull from all three bureaus — Experian, Equifax and TransUnion — then typically work from the middle of the three.
So your free app says 740, your mortgage score comes back 712, and nobody did anything wrong. Expect some difference and do not be alarmed by it.
What actually drives the score
Payment history is the largest factor. One 30-day late payment can cost a surprising number of points, and recent misses weigh more than old ones.
Amounts owed — specifically your credit utilization, the balance on your revolving accounts against their limits. This is the fastest lever you control. Paying a card from near its limit down to a small balance can move your score within a cycle or two.
Length of credit history. Older accounts help. This is why closing your oldest card to tidy things up is counterproductive.
Credit mix and new credit. Smaller factors. A reasonable mix of account types helps slightly; a flurry of new applications hurts slightly.
What to do before you apply
Pull your reports and check them. You are entitled to free copies from the official annual credit report service. Errors are common — accounts that are not yours, balances that were paid, old items that should have aged off. Disputing them takes time, which is why this is a job for several months before you buy, not the week you start looking.
Pay down revolving balances. The highest-return action available to most people.
Keep old accounts open. Even unused ones. They are helping.
Stop opening things. No store cards, no new financing, nothing.
Pay everything on time, without exception.
Be careful who you take advice from
Credit repair services that promise dramatic quick results are generally selling something you could do yourself for free, and some of what they do — disputing accurate items en masse — can backfire. Legitimate errors are worth disputing. Accurate negative information will age off on its own schedule and cannot be removed by paying someone.
Talk to a mortgage lender early even if your credit is imperfect. A good loan officer will tell you specifically what to address and roughly what it is worth, which beats guessing. Many buyers are closer to qualifying than they assume.
And once you are approved
Everything above still applies right up to the day you get the keys. Your lender will check again before funding. There is a separate article on this site about what not to do between offer and closing — it is worth five minutes.