According to a recent CardHub.com study, in the absence of a true credit limit, issuers report to credit bureaus either the highest balance reached with an NPSL card over a certain period of time or its revolving credit limit for the determination of credit utilization.

FORBES: The Pitfalls of No Pre-Set Spending Limit Credit Cards

Because of the importance of a credit limit to your credit score and the lack of a communicated limit to consumers, the question must be posed: How does FICO determine credit utilization on NPSL cards when there is no credit limit?

FORBES: The Pitfalls of No Pre-Set Spending Limit Credit Cards

Similarly, if a high balance is reported as your credit limit and your spending is fairly consistent, your utilization ratio will hover near 100% on a monthly basis as well.

FORBES: The Pitfalls of No Pre-Set Spending Limit Credit Cards