How do I fix OHIP error code AC4?

Find the referral letter or requisition and confirm who referred the patient. Enter the referring provider's six-digit OHIP number, not your own. If a nurse practitioner or midwife made the referral, check the Schedule of Benefits to confirm the fee code can be billed on that referral. If it can't, bill only a code whose requirements the service actually meets. Resubmit the corrected claim. If more than three months have passed since the service date and the original claim was sent on time, use the stale-dated claim process described under VJ7.

When shouldn't I resubmit a AC4 claim?

There was no referral. Entering a number does not make a consultation billable. You can't identify the referring provider. Never enter a placeholder or your own number.

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Error code

AC4 — Unaccepted Referral Number

Q: What does OHIP error code AC4 mean?

AC4 means OHIP did not accept the referring provider number on the claim. It may be missing, not six digits, or not allowed for this fee code.

Referring number not accepted

OHIP didn't accept the referring provider number: it may be missing, not six digits, or not allowed for this fee code.

What to do: Check the referral letter and enter the referring provider's six-digit OHIP number, not your own.

Code: AC4
Description: Unaccepted Referral Number

Explanation

Updated October 26, 2026

AC4 means OHIP did not accept the referring provider number on the claim. It may be missing, not six digits, or not allowed for this fee code.

What it means

Some services are only paid when another health care provider referred the patient. Consultations, repeat consultations and limited consultations are the most common examples. These claims need the referring provider's six-digit OHIP number in the referring provider field.

OHIP rejects the claim with AC4 when that number is not acceptable. The Ministry's rejection list gives these reasons: the number is not six digits; it is the same as the billing physician's own number; or it belongs to a nurse practitioner or midwife and the fee code can't be billed on a referral from that type of provider.

Common causes

The referring provider number was left blank.
A typing error left the number short or wrong.
The billing physician's own number was entered as the referrer.
A nurse practitioner or midwife referred the patient for a service that needs a referral from a different type of provider.

How to fix it

Find the referral letter or requisition and confirm who referred the patient.
Enter the referring provider's six-digit OHIP number, not your own.
If a nurse practitioner or midwife made the referral, check the Schedule of Benefits to confirm the fee code can be billed on that referral. If it can't, bill only a code whose requirements the service actually meets.
Resubmit the corrected claim. If more than three months have passed since the service date and the original claim was sent on time, use the stale-dated claim process described under VJ7.

Don't resubmit if

There was no referral. Entering a number does not make a consultation billable.
You can't identify the referring provider. Never enter a placeholder or your own number.

How APEX handles it

APEX lists AC4 claims in the Correction Centre as needing your input. You enter the referring provider's six-digit number and APEX resubmits the original claim with it. This works for every specialty. See how APEX works · Pricing

Related codes: V09