By Danielle Leigh
(NBC) - If you haven't checked your credit score lately, you may want to.
A new study by the Federal Trade Commission indicates as many as 40 million Americans have errors on their credit reports.
Those errors can keep you from getting a loan, qualifying for lower interest rates and even cost you a job.
Tawanna Sellers is one of the roughly 20 percent of Americans with an inaccurate credit report.
The food service employee discovered the errors only after she was denied a loan to start a food truck company last year.
Months later she's still fighting to fix her credit.
"Sometimes I think they want you to get frustrated so you stop, but I can't," she says.
Three companies dominate the credit reporting industry: Equifax, TransUnion and Experian.
They determine your credit score based on how you've paid your bills and how much debt you have.
In a statement an Experian spokesman said the agency takes "all errors seriously" adding: "The vast majority of disputes are resolved in 14 days or less."
"Some rate of error is to be expected, and what is important to focus on is when an error identified whether or not it is fixed," says the Federal Trade Commission's Beth Freeborn.
The latest study by the FTC found agencies modify disputed errors 90 percent of the time.
Mattias Kraemer of the Latino Economic Development Center helps people navigate that process.
"The process is not a one and done," he warns. "You've got to insist, you've got to commit. Maybe you're going to have to write the letters again."
Kraemer advises people to take advantage of free yearly credit checks and dispute any errors immediately.
Tawanna Sellers is taking that advice and says she is seeing progress.
Only two out of a handful of errors still remain on her report.
Consumers who are unable to resolve errors on their credit do have a recent- added layer of protection.
Late last year the Consumer Financial Protection Bureau began supervising large credit agencies to insure consumer concerns get addressed.