Building a strong credit score may seem like a complicated undertaking, but it generally involves making informed choices and avoiding common pitfalls. When you don’t know what behaviors to avoid, you could be dragging down your credit score without knowing it.

Don’t let unintended blunders hurt your credit. Here are seven common credit mistakes to avoid.

1. Making Late Payments

Payment history is the single biggest contributor to your credit, making up 35% of your FICO credit score. Just one late payment on your credit report can cause your credit score to drop significantly, especially if you previously had an excellent score. The single biggest credit mistake you can make is to not pay your bills on time.

It’s important to remember that late payments won’t be reported to the credit bureaus until at least 30 days after the due date – and the later they get, the more damage they can do. So even if you’ve already missed a payment, you can prevent further damage (or avoid damage altogether) by making the payment ASAP.

2. Maxing Out Credit Cards

The “Amounts Owed” category makes up 30% of your credit score. While having a large amount of debt won’t necessarily hurt your credit, using up too much of your available credit can be harmful. It’s a good idea to stay far away from your credit card’s limit for this reason.

Your credit utilization ratio tells creditors how much of your available credit you have tied up in debt – for example, if you have a credit card with a $1,000 limit and a balance of $500, your credit utilization for that card is 50%. Maxing out your credit cards will drive that ratio too high and can lower your credit score, so try to maintain a low balance.

3. Closing Old Credit Cards

If you no longer use an old credit card, you may be tempted to close it out to keep things simple. But unless you’re in financial trouble and can’t responsibly manage credit, you should always keep your old cards open.

That’s because the length of your credit history makes up 15% of your credit score. Typically, a longer credit history leads to a stronger credit score. Closing old cards will lower the average age of your accounts and you’ll no longer get the credit boost from those old credit cards.

4. Opening Too Many Accounts at Once

Whether you’re applying for loans, credit cards, or both, opening too many credit accounts in a short amount of time makes you appear risky to creditors and can lower your credit score. If you plan on opening multiple new credit accounts, try to space out your applications as much as possible.

5. Cosigning a Loan

Even when you trust the person you’re helping, cosigning someone else’s credit card or loan is a very risky move. Essentially, you’re tying your own credit score and credit history to someone who may or may not be able to pay their bills on time.

When you cosign a loan, you’re taking on shared responsibility with the applicant. If they don’t make their payments, that information lands on your credit report and you could even be held responsible for the debt in question.

6. Ignoring Your Credit

It’s easy to ignore your credit if you don’t understand why it’s important. But monitoring your credit report and credit score is an important aspect of your financial health. Ignoring your credit could keep you from getting a credit card, buying a car, owning a home, and more.

Monitoring your credit doesn’t have to a be difficult, time consuming task. You’re entitled to a free copy of your credit reports once a year, and you can even outsource the work to a identity and credit monitoring agency who can monitor you credit and provide additional identity protection services to boot.

7. Living Beyond Your Means

Creditors aren’t giving out free money. Taking on debt you can’t afford can lead your finances and credit to spiral out of control. Never buy or borrow beyond your means, as it could lead to much greater financial woes in the future.