In medical billing, DOS is an acronym for what?

• A. Date of Service
• B. Date of Submission
• C. Date of Source
• D. Date of Settlement

Answer: (A)

Date of Service means the actual date when the medical service or encounter occurred. This date links the CPT/HCPCS codes to the specific care provided and is used to determine eligibility, payer timing rules, and the correct sequencing of services on a claim. If there are multiple services on different days, each service line will have its own Date of Service. The Date of Submission refers to when the claim is sent to the payer, not when care happened, and Date of Source isn’t a standard billing term. Date of Settlement relates to when payment is resolved, not the timing of the service itself.