MA31 remark code

Remittance advice remark code MA31. Remark codes add detail to the reason code on the same claim line.

Missing or invalid billing period dates

Unofficial reference. This is our own plain-English explanation, not the official code text. Payer rules differ. Verify with the payer and the official X12 code list. AlphaPrefix is not affiliated with X12, CMS or any payer. Data last updated Nov 11, 2026.

What MA31 means

The from and through dates for the billing period are missing, incomplete or do not make sense together.

The payer needs a clear statement period on the claim. This remark says the start or end date was missing, invalid, reversed, or conflicts with the service dates on the lines.

It usually comes with reason code 16 and is fixed with a corrected claim.

Common causes

• The through date is earlier than the from date.
• Line dates of service fall outside the statement period.
• The period spans dates that the payer requires to be split onto separate claims.

What to do next

1. Check the statement period against every line date of service.
2. Split the claim if the payer requires separate periods.
3. Send a corrected claim with valid dates.

Related codes

• 16 (reason code) Missing information or billing error
• MA30 (remark code) Missing or invalid type of bill
• MA40 (remark code) Missing or invalid admission date