Answer: One cardinal rule of job-seeking is that you should never surprise a potential employer with bad news. If you feel fairly certain that negative information will be unearthed, it’s wise to provide a heads-up. But don’t launch into a detailed recounting of your financial woes. Just offer a simple, straightforward explanation.
For example: "Since you may do a credit check, I wanted to let you know that I did get into debt for medical bills at a time when I had no health insurance. I'm working my way out of this problem, but it still shows up on my record."
You will usually know when a credit check is planned, because federal law requires that applicants be given advance notice. Even if a job has no financial responsibilities, your credit history may still be considered as an indicator of your judgment, so you definitely want to influence how the report will be interpreted.
Do interviews make you nervous? Here are some tips that may help: How to Conquer Interview Anxiety.