Shopping lenders is the most reliable way to cut the cost of a loan. On any given morning the gap between the highest and lowest posted 30-year mortgage rates across lenders is wider than the market moves that day: on September 1, 2026 it was 1.25 points across the lenders RateZip tracks, roughly $325 a month on a $400,000 loan. But every formal application puts a hard inquiry on your credit report, and the fear that a pile of inquiries will sink your score keeps a lot of people from shopping at all. The scoring models anticipated this and built in a grace window. The catch is that the folk version of the rule — “get all your applications in within 30 days” — is wrong, and following it can cost you.

Why applying for credit touches your score at all

New credit accounts for 10% of a FICO score. A hard inquiry is the record a lender leaves when it pulls your file because you asked to borrow. Statistically, someone opening a lot of new accounts in a short stretch is a riskier borrower, so the model treats a burst of inquiries as a warning sign. Rate shopping looks the same on paper — several lenders pulling your report in a few weeks — but it is one loan, not several. Both major scoring companies handle that distinction with a deduplication window: inquiries of the same type that fall inside the window count as a single inquiry.

What the models actually do

  • FICO: mortgage, auto and student-loan inquiries that land inside a 45-day window count as one on current versions of the score. Older versions still in use at some lenders use a 14-day window. On top of that, FICO ignores any inquiry less than 30 days old when it calculates your score.
  • VantageScore: a 14-day window, and it groups every type of inquiry, not just loans.
  • Credit cards: FICO never groups card applications. Three card applications are three inquiries, no matter how close together they fall.

Where the “30 days” came from, and why it misleads

The 30-day number is real; it is just the wrong takeaway. Because FICO disregards inquiries younger than 30 days, a fresh cluster of applications is invisible to your score while you are still shopping and while the lender you pick is underwriting you. That is the grace period. Once the inquiries age past 30 days they start to count, and whether they count as one or as several depends on the deduplication window. If you spaced your applications across a full month, you blew through the 14-day window that older FICO versions and VantageScore use, and some of those inquiries now count separately. The 30-day rule protects you during the shop and then quietly fails you afterward.

The practical rule: finish in 14 days

You do not get to choose which score version a lender pulls. Since April 22, 2026, lenders selling loans to Fannie Mae and Freddie Mac may use FICO 10T or VantageScore 4.0, but the switch is optional, so older versions remain in use alongside the new ones. The only window that satisfies every model at once is the shortest one. Do your formal applications inside 14 days and it does not matter whose score gets pulled: the inquiries collapse into one.

How to run a two-week shop

  • Get the paperwork together first. Recent pay stubs, tax returns, bank statements, ID. The clock starts with your first application, not your first phone call, so do the slow part before you apply anywhere.
  • Vet lenders before you apply. Compare posted rates and fees, read reviews, and use prequalification tools that rely on a soft pull to narrow the field. Only formal applications create hard inquiries.
  • Apply in a tight cluster. A handful of formal applications in the same week is ideal. For a mortgage, every lender must deliver a Loan Estimate within three business days of your application, so comparable offers arrive fast.
  • Do not open a credit card mid-shop. Card inquiries are never grouped, and a brand-new account changes your profile while an underwriter is looking at it.
  • Check your reports before you start. They are free every week from all three bureaus at AnnualCreditReport.com. Find and dispute errors before a lender finds them.

What a hard inquiry really costs

Less than most people fear. Inquiries are one piece of the new-credit factor, which is itself one of the smallest pieces of the score, and their effect fades with time. The real damage from loan shopping is not the inquiries; it is what people do around them — opening new cards, running up balances to cover moving costs, or missing a payment in the chaos of a purchase. Payment history and how much of your available credit you are using are the two factors that matter most, and both are entirely in your control while you shop. If your score is stuck for other reasons, the three mistakes that genuinely hurt it are worth a read, and the mechanics behind each factor are laid out in how credit scores work.

Shop hard, shop fast, and shop once. Two weeks of concentrated effort gets you the best rate available to you, with a credit score that comes out the other side essentially untouched.