Glossary
Case number
The unique identifier assigned to a case when it's filed. Often encodes the year, the type of case, and a sequential number: formats vary by court.
Case numbers look different in different courts, but most include the year of filing and a code for the case type. For example, a federal civil case in the Middle District of Tennessee might be 3:24-cv-00481 (district 3, year 2024, "cv" for civil, sequence number).
If you're filing anything in a case, the case number goes in the caption (the heading) of every document. Without it, the clerk has no way to route your filing to the right file.