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M46 Remark Code: Occurrence Span Code Invalid

M46 means the payer could not process the claim because an occurrence span code, which reports an event covering a range of dates, is missing, incomplete, or invalid.

Quick facts

Code
M46 (RARC M46)
Status
Active In use since January 1, 1997; last modified December 2, 2004.
Code set
Remittance Advice Remark Codes (RARC)
Group codes
  • CO (Contractual Obligation): The claim remains unpaid until the span code is corrected. The patient is not billed.
Official description
Missing/incomplete/invalid occurrence span code(s).
X12 Remittance Advice Remark Codes, retrieved September 25, 2026
Last verified
against the official X12 list.

What M46 means

Where an occurrence code marks a single date, an occurrence span code marks a period with a start and end date. Institutional providers use span codes to report things like a qualifying hospital stay before skilled nursing care, or days during a stay that were not covered. M46 says the payer needed one of these spans and it was missing, or the code or its structure was invalid.

Skilled nursing facilities and hospitals see M46 most often, since their coverage rules depend on date ranges.

Common causes

  • A SNF claim did not report the qualifying stay span.
  • The through date is earlier than the from date, or outside the statement period.
  • A span code was reported with only one date.
  • An outdated or bill-type-inappropriate span code was used.

How to fix it

  1. Identify the required span from the payer’s billing guidance for your bill type.
  2. Correct form locators 35-36 with a valid code and a logical date range.
  3. Cross-check the statement covers period (form locator 6) and admission dates.
  4. Resubmit following the payer’s process for returned or adjusted claims.

How to prevent it

Build edits that compare span dates to the claim’s statement period and admission data, and keep span code tables current. Data errors like this are reviewed in claim rejection vs denial.

Codes that may appear with M46

  • CO-16 (Claim/service lacks information or has submission/billing error(s).): Information needed to process the claim is missing or invalid.
  • N300 (Missing/incomplete/invalid occurrence span date(s).): The span dates are missing or invalid, rather than the code.
  • M45 (Missing/incomplete/invalid occurrence code(s).): A single-date occurrence code is missing or invalid.
  • M49 (Missing/incomplete/invalid value code(s) or amount(s).): A value code or amount is missing or invalid.

M46 FAQ

Where do occurrence span codes go on the UB-04?

In form locators 35 and 36, each with a code and a from and through date.

What kinds of periods do span codes report?

Examples include qualifying stay dates for skilled nursing coverage, periods of non-covered days, and other date ranges defined by the National Uniform Billing Committee.

What if the dates overlap the claim period incorrectly?

The payer may reject the span code as invalid. Check that the from and through dates are logical and fit the claim's statement period.