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Error code

HM — Invalid master number on service date

Invalid hospital number

The hospital master number on the claim wasn't valid on the service date.

What to do: Check the master number against the hospital's current number and correct it in your billing software.

Code
HM
Description
Invalid master number on service date

Explanation

Updated October 26, 2026

HM: the hospital (master) number on the claim wasn't valid on the service date. Check the master number for the facility.

What it means

HM means the master number on the claim was not valid on the date of service. The master number is the Ministry's number for the hospital or facility where the service was given.

Common causes

  • A typing error in the master number
  • An old master number used after a hospital merger or renumbering
  • The master number of a different site or facility

How to fix it

  1. Check the master number on the claim against the hospital's current number.
  2. Correct it in your billing software so future claims use the right one.
  3. For this claim, if it was not paid, send a Remittance Advice Inquiry (RAI) through eSubmit, or on form 0918-84, within 7 months of the RA date, with the correct master number.

How APEX handles it

APEX reads your error reports and remittance advice from MCEDT and lists claims rejected with this code in its Correction Centre for you to correct and resubmit. See how APEX works · Pricing

Related codes: H8, AH8, V28, EQK

Sources