Primary tradelines refer to credit accounts that are reported to the credit bureaus under your name. These include credit cards, auto loans, mortgages, and other types of installment loans. When you become a primary user on someone else's credit account, it gets added to your credit report as a primary tradeline. This can give your credit score a boost by improving your credit mix, lowering your utilization rate, and increasing the average age of your accounts. More importantly, primary tradelines demonstrate that you have a positive track record of managing credit responsibly. So by adding primary tradelines to your thin credit file, you improve your chances of getting approved for loans and other credit products you apply for. The additional positive history helps offset limited credit or any negative marks you may have. With the right primary tradelines boosting your credit profile, you can qualify for the financing you need.