Understanding Credit Scores: What Mortgage Underwriters Really Look For
Have you ever wondered how a credit score is determined? You’re not alone.
You’ve probably heard that your credit score can make or break your mortgage application. But what does that number really mean — and what’s going on behind the scenes when a lender pulls your credit?
As a mortgage underwriter with over three decades of experience, I’ve seen the full spectrum of credit reports. Let me walk you through what matters most, what doesn’t, and how to put your best foot forward when applying for a mortgage.
What Is a Credit Score, Really?
A credit score is a three-digit number that gives lenders a snapshot of your creditworthiness. It’s calculated based on the information in your credit report and typically falls between 300 and 850. The higher the score, the lower the risk — at least in theory.
But here’s what many consumers don’t realize: you don’t have just one credit score. Mortgage lenders usually pull what’s called a tri-merge credit report or Mortgage Credit Report — one that includes scores from all three major credit bureaus: Equifax, Experian, and TransUnion. Each bureau may report a different score depending on what data it has, and lenders usually use the middle score when evaluating your application.
How Is a Credit Score Calculated?
Credit scoring isn’t an exact science — at least not from the consumer’s side. While it might feel like there’s a secret formula, the truth is, credit scores are calculated using a combination of factors:
Your payment history
How much of your available credit you’re using
The length of your credit history
The types of credit you have (credit cards vs. loans)
Any recent credit activity
Collection accounts — even small or paid ones — can still hurt your score, though their impact typically fades over time.
Each credit bureau uses its own scoring model, and those models can change. That’s why scores vary between bureaus and why it’s nearly impossible to predict your exact number.
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How Credit Scores Impact Your Mortgage
Credit scores affect more than just whether or not you get approved — they can also influence your interest rate, your loan options, and even how much you’ll need for a down payment.
Generally:
740+ is considered excellent
700–739 is very good
660–699 is good
620–659 is fair
Below 620 is considered unfavorable (but not necessarily a deal-breaker)
Most conventional loan programs require a minimum score of 620, but FHA loans allow scores as low as 580 with a 3.5% down payment — and as low as 500 with a 10% down payment and strong compensating factors. That’s where an experienced underwriter steps in to assess the full picture.
What Underwriters Actually Look For
Here’s a little industry secret: it’s not just about the score. A high credit score might come with red flags, and a lower score isn’t always a sign of trouble. As an underwriter, I always look deeper.
Key things we pay attention to:
Payment history – Have you paid on time? Any late payments in the last 12–24 months?
Credit utilization – How much of your available credit are you using?
Length of credit history – Older accounts are better for your score.
Credit mix – A healthy mix of revolving (credit cards) and installment (such as car or student loans) credit is ideal.
Recent inquiries – Excessive credit checks raise concerns. You’ll be asked to explain any inquiries from within the past 120 days.
We also consider the story behind the numbers. A one-time medical collection is very different from multiple missed credit card payments over time. (Note: Most medical collections are no longer considered in underwriting decisions.)
What If I Don’t Have a Credit Score?
Some people simply don’t use credit and therefore don’t have a credit score at all. That doesn’t mean you’re out of luck when it comes to getting a mortgage.
While many loan programs require a score, there are options available for borrowers without one, including programs that accept alternative credit — such as on-time rent, utility, phone, or insurance payments.
We won’t go into those guidelines here, but it’s important to know that a lack of a credit score doesn’t automatically disqualify you. Talk to a loan officer who understands the available programs — and how to document your financial reliability in other ways.
A Note on Credit Karma and Other Consumer Sites
Sites like Credit Karma offer free scores, but they’re usually VantageScores, not the FICO models used by most mortgage lenders. These can differ — sometimes by a lot.
If you want a true sense of where you stand before applying for a mortgage, request a full copy of your credit report from AnnualCreditReport.com, which offers one free report per bureau every 12 months.
(If you’re denied credit, you may also be eligible for a free report within 60 days of that decision.)
What You Can Do to Strengthen Your Score
Pay on time, every time. Payment history is the biggest factor.
Keep balances low on credit cards and revolving lines.
Avoid opening new accounts before or during the mortgage process.
Don’t close old accounts unless there’s a good reason — they help your length of credit history.
Address errors early — dispute incorrect information well in advance of applying.
Final Thoughts
Your credit score is one piece of the mortgage puzzle — but it’s not the whole picture. A good underwriter (and a good loan officer) will look at the entire story, not just the numbers.
If you’re planning to apply for a mortgage soon, it’s worth doing a little credit housekeeping now. And if your score isn’t perfect, don’t panic. I've approved many loans where the credit score didn’t tell the full story — because that’s what underwriting is really about.
