OHIP error code AC4: unaccepted referring provider number

Why it fires

• The referring number is not exactly six digits.
• The referring number is the same as your own billing number (self-referral on a code that does not allow it).
• The number falls in the nurse practitioner range (722900-744292) and the fee schedule code is not eligible for an NP referral.
• The number falls in the midwife range (700000-722899) and the fee schedule code is not eligible for a midwife referral.

AC4 is an assessment error on the Claims Error Report. The claim never reaches the remittance advice as a paid item. The Ministry publishes four concrete rejection reasons: the number is not six numerics, it equals the billing practitioner number, it is an NP number used on a code that does not accept NP referrals, or it is a midwife number used on a code that does not accept midwife referrals.

For specialists this usually surfaces on consultations, e-consults, and diagnostic services that have a technical and professional component. Those listings require a referring or requisitioning health care provider number. A family physician number that is six digits and currently registered will generally pass this check. An NP or midwife number will pass only when the Schedule listing for that fee code allows that referrer type.

A common clinic pattern is copying a referrer from the EMR address book that was stored as five digits, with a missing leading zero, or stored as a CPSO number rather than the six-digit OHIP billing number. Another pattern is using your own number because the patient arrived without a letter and the software required a value in the field. AC4 is the Ministry saying that value is not an accepted referral for this service code.

What it costs

The claim is rejected outright. Nothing is paid until a corrected claim is accepted. The amount at risk is the full fee for that consultation or diagnostic service, which varies by fee schedule code.

Unlike some remittance-advice adjustments, AC4 does not pay a reduced visit in the same cycle. The item is off the payment run. If the practice does not correct and resubmit, the entire professional fee for that encounter is unpaid.

Consultation listings are the high-value cases. A single missed consult for internal medicine, psychiatry, or neurology is a full consult fee, not a clerical nuisance. Diagnostic requisitions (spirometry, ECG professional component, imaging professional fees) add a second loss if those claims need a requisitioning number and carry the same AC4.

How to fix it going forward

• Store referring providers in the EMR by six-digit OHIP billing number, not CPSO number or truncated digits.
• Block self-referral on consultation and requisition codes unless the Schedule listing explicitly allows it.
• When the referrer is an NP or midwife, confirm the fee schedule code is on the Ministry list that accepts that referrer type before you submit.
• Train booking staff to capture the referrer number from the consultation request, not from memory or a stale address book row.

The durable fix is data quality in the referrer file, not a one-off resubmit. Review address-book records that fail AC4 twice. Those rows are usually wrong in the same way every time: five digits, a group number, or a student/trainee identifier.

For NP and midwife referrals, keep a short internal list of the consultation and laboratory codes your group actually uses that accept those referrer ranges. Do not assume every specialist consult listing accepts an NP. The Ministry lists the eligible fee schedule codes; using any other code with an NP or midwife number is a designed AC4.

Is it recoverable?

Recoverable by resubmission inside the window

Correct the referring number (or the fee schedule code, if the referrer type is the constraint) and resubmit inside the three-month window from the date of service.

If the original claim reached the Claims Error Report inside three months of the service date, a corrected resubmission remains the first path. Replace the number with the six-digit billing number from the written consultation request. If the only available referrer is an NP or midwife and the code you billed does not accept that range, you need a different eligible code or a physician referrer. Do not keep resubmitting the same pair.

Once the three-month window has closed and the claim was never accepted, payment is not automatic. The claim may be recoverable by written application to the Ministry where documentation supports it. That is a separate process from a routine resubmit.

Related codes

• EQ6: referring provider number not registered
• ERF: referring physician number currently ineligible
• V09: referring provider number invalid
• AEV: visit only allowed

Frequently asked questions

What does OHIP error code AC4 mean?

AC4 means the referring or requisitioning provider number on the claim is unaccepted. The Ministry rejects numbers that are not six digits, that match your own billing number, or that belong to a nurse practitioner or midwife on a fee schedule code that does not allow that referrer type.

Can I resubmit an AC4 claim with the same referring number?

Only if the original rejection was a format problem you have now fixed, such as restoring a leading zero. If the number is an NP or midwife number on a code that does not accept that range, resubmitting the same pair will produce AC4 again.

Is AC4 the same as a missing referring number?

No. A missing referring physician number is a different error (ARF or ARP on the Ministry list). AC4 means a number was present and was not accepted for this service code.