Does "bad credit" affect postdoc application in math? Does a bad credit score affect my chance in applying for a postdoc in math? In my case, I have a credit card that had the bill sent to the wrong address and this impacted my score with all three credit agencies.
I have a lot of experience with postdoc hiring in mathematics at several institutions.  There is no mechanism by which faculty who are reading postdoc files would know your credit score, so you shouldn't worry that it will affect your application.  

HR departments don't really play a role in academic job searches (aside from technical things like approving the wording of job ads).  It is all done by academics.  So though in the private sector HR departments do things like run credit searches, this just doesn't happen during faculty and postdoc searches at universities.