Box 3: Patient birth date and sex
By Dr. Daniel Turner, DC · Reviewed September 2, 2026
What goes in Box 3 of the CMS-1500?
The patient’s date of birth in MM DD YYYY and their sex as recorded by the payer. It is an identity match field: the payer checks it against the member record.
What does Box 3 mean for chiropractic billing?
A birth date typo is one of the quietest claim killers in a chiropractic office, because everything else on the claim is right and the denial reads like a mystery. When a patient not found denial appears with a correct ID, check this box next.
The mistakes that turn this box into denials
- ✗Month and day transposed at intake
- ✗A dependent’s claim carrying the subscriber’s birth date
The denials this box causes
How Cervica fills Box 3
Cervica generates the CMS-1500 and its electronic 837P equivalent from the chart and the payer's own rules: identifiers from the verified insurance record, modifiers and codes per payer, and pre submission scrubbing that flags exactly the mistakes listed above before a claim leaves the building.
Related boxes
- →Box 2 · Patient name
- →Box 1 and 1a · Insurance type and insured ID number
General information for billing teams, not billing advice for any individual claim. The NUCC's 1500 Claim Form instructions and each payer's companion guides control.