Some money mistakes cost you a late fee. A few quietly follow you for years — and your credit score, the number between 300 and 850 that sets the price you pay on every mortgage, car loan and card, is where they show up. The formula is not a mystery: payment history counts for 35% of a FICO score, amounts owed 30%, length of credit history 15%, and new credit and credit mix 10% each. Which means the three mistakes below, touching 80% of the formula between them, do most of the damage.

Mistake #1: Paying bills late

The largest single slice of your score — 35% — is your record of paying on time. A late payment here and there feels minor, but the marks accumulate, and a strong payment history is slow to build and quick to dent. The fix is structural, not motivational: put every account on autopay for at least the minimum, then pay the rest manually when you review the statement. A payment that cannot be forgotten is a payment that cannot go late — no excuses required, because the system does the remembering. And if a bill does slip through, pay it the moment you notice: the further past due a payment goes, the more damage it does.

Mistake #2: Charging up your credit cards

The second-largest slice — 30% — is amounts owed, and for most people that means credit utilization: the share of your available credit you are actually using. The guidance is simple: keep utilization below 30% of your limits, and lower is better still. High balances drag on your score even when every payment arrives on time, which surprises a lot of diligent people. So watch the ratio, not just the due date — and if you are carrying balances at 2026 card rates, paying them down does double duty, cutting interest and lifting your score at once. The playbook for that is in our credit card APR escape plan.

Mistake #3: Avoiding credit entirely

Plenty of careful people swear off credit cards and loans on principle — then discover the caution has a cost. Length of credit history is 15% of your score, and you cannot build history you never start; a thin file can hold you back almost as much as a blemished one when it is time for an apartment, a car loan or a mortgage. The modern on-ramps are low-risk:

  • Become an authorized user on a card belonging to a family member with a long, clean record. The account's on-time history goes to work on your file without your borrowing a dollar.
  • Open a secured card. A refundable deposit sets your limit, and several major issuers now offer $0-annual-fee secured cards with automatic reviews that can graduate you to a regular unsecured card. Put one small bill on it and pay in full every month. How secured cards differ from prepaid debit — and why only one of them builds credit — is covered in Secured Credit Card vs. Prepaid Debit Card.

Whichever on-ramp you choose, resist opening several accounts at once. New credit is its own 10% slice of the formula, and a burst of applications works against the history you are trying to build.

Check your work — it's free

Every one of these mistakes appears on your credit reports before it becomes a score you don't like, and the reports cost nothing: you can pull them from all three bureaus every week at AnnualCreditReport.com. Scan for late marks you don't recognize, balances that look wrong, and accounts you never opened.

The good news about most money mistakes is that they are fixable. Late marks age, utilization resets as balances fall, and history builds on its own once the accounts exist. Set up the autopay, watch the ratio, get the file started — the score follows the habits.