The phrase "first delinquency" refers to the initial time or instance when someone fails to do something they are supposed to do or breaks a rule or law.
The filing date can be years after your hospital admission, and years after your date of first delinquency on the original invoice. (growingfamilybenefits.com)
Any negative experience stays on your consumer file for 7 years — counting from the date of first delinquency on each account. (growingfamilybenefits.com)
Sometimes the source does not convey the correct date of first delinquency. (growingfamilybenefits.com)