OHIP error code AT3: what it means and how to fix it

AT3 means OHIP cannot verify an established patient-physician relationship. Specifically, it cannot find a physical in-person encounter within the 24 months preceding the service date. If you are staring at an AT3 rejection right now, you have not necessarily billed incorrectly. OHIP's system simply cannot confirm the relationship meets its threshold, and the burden of proof lands on your practice.

That distinction matters, because the fix is different depending on whether the relationship actually exists and your documentation proves it, or whether the 24-month window has genuinely lapsed.

Here is everything you need to know to resolve an AT3 rejection and keep it from recurring.

AT3 at a glance: no patient-physician relationship

AT3 is an A-series Error Report code, meaning the claim is rejected at the point of validation before payment is processed. It never reaches the Remittance Advice stage as a paid or adjusted claim.¹

The official MOH description is: "No patient-physician relationship."²

In practice, that means OHIP's system searched for a qualifying in-person encounter between the billing physician and the patient within the previous 24 months and found none on record. The claim cannot proceed until that relationship is verified or the documentation is escalated for manual review.

A common misconception is that AT3 flags fraud or intentional over-billing. It does not. In most cases we review, it reflects a documentation gap or a billing workflow that outpaced the patient's visit history. That is especially common when practices shift toward virtual-first care.

The 24-month encounter rule: what OHIP actually requires

OHIP's patient-physician relationship requirement has always existed in the Schedule of Benefits, but it became a front-line issue for most practices only after virtual care scaled rapidly post-2020. The rule is straightforward when you know it exists: a qualifying physical encounter between physician and patient must have occurred within 24 months of the service date being billed.

If you are billing on June 15, 2026, OHIP looks for a documented in-person visit on or after June 15, 2024.

What does not count toward that 24-month window:

Telephone consultations
Video or virtual care visits
Patient portal messages or e-prescribing contacts
Referral letters or consultation reports from other providers

Virtual care sits in a specific grey zone. A virtual encounter can be billed successfully if the patient-physician relationship was already established through a prior in-person visit within the window. But a practice that has seen a patient exclusively by video, as many did during the height of the pandemic, may have no qualifying physical encounter on record at all. That is the exact scenario AT3 was designed to catch, and it is why AT3 rejection rates have tracked closely with telehealth adoption since 2021.³

The B3 Remittance Advice explanation code ("Patient-Physician Relationship Requirements Not Met") is a related flag that can appear when a claim clears initial validation but is adjusted on the RA. AT3 and B3 are not interchangeable. AT3 stops the claim at Error Report and B3 appears post-adjudication, but they share the same root cause.¹

Root causes: why AT3 is appearing on your claims

Based on the billing data we review across Ontario specialist practices, AT3 tends to cluster around four scenarios:

1. A new patient was seen virtually without a prior in-person baseline. The patient was referred, you assessed them by video, and the billing went through your normal workflow. No one flagged that there was no in-person chart note on file because that step felt routine.

2. A previously active patient went quiet for more than 24 months. Life happens. Patients move, delay follow-ups, or switch providers without notifying your clinic. When they return, often virtually, the 24-month window has expired.

3. Practices switched to virtual-first workflows without updating intake protocols. This was nearly universal between 2020 and 2023. The billing codes changed rapidly. The underlying relationship rules did not.

4. Chart documentation is incomplete or lacks a visit timestamp that OHIP can verify. Even when the in-person visit happened, a chart note that is not finalized, not dated clearly, or not linked to the correct OHIP billing number may not satisfy adjudication.

Practices managing their own billing or using less structured EMR workflows tend to see AT3 appear in 5–8% of their rejection volumes. Practices with professional billing oversight typically run below 2%.³ That gap is almost entirely attributable to documentation hygiene and intake protocols, not to differences in care delivery.

If you want to understand what OHIP's broader billing framework looks like before you get to error codes, what medical school did not teach you about OHIP and Medicare billing is a useful starting point for context.

Step-by-step: how to fix an AT3 rejection

Work through these steps in order. The 3-month resubmission window from the service date applies, so do not wait.

Step 1: Pull the patient's chart and confirm encounter history. Look for any in-person visit dated within 24 months of the rejected service date. Check both your primary EMR and any paper records, especially if the patient transferred from another provider or was seen at a different clinic location.

Step 2: Confirm the visit note is complete and dated. A chart entry must include a clinical assessment and a finalized timestamp. Progress notes flagged as drafts, unsigned, or missing the date of service may not be accepted as evidence.

Step 3: If a qualifying visit exists, resubmit the corrected claim. Include the encounter date in your resubmission documentation. If your EMR or billing software allows it, attach the supporting chart note or flag the claim for manual review. This is not an appeal. It is a corrected submission with evidence. OHIP adjudicators can confirm the relationship and process payment.

Step 4: If no qualifying in-person visit exists, assess your options. You have two paths. First, you can schedule the patient for an in-person encounter, establish the relationship, and then bill future virtual services against that documented baseline. Second, if you believe special circumstances apply, you can submit a manual review request with a clinical narrative explaining the situation. Manual review does not guarantee payment, but it puts the decision in human hands rather than automated adjudication.

Step 5: Track the resubmission outcome. Log the original rejection date, resubmission date, and adjudication result. This data tells you whether your documentation approach is working and helps identify whether AT3 is a one-off or a pattern.

The OMA's March 2026 "Let's Fix OHIP" campaign noted that approximately 1.16 million claims annually require manual review across Ontario, a volume that reflects systemic friction in OHIP's adjudication process rather than individual physician error.⁴ AT3 is one of the codes contributing to that number.

Preventing AT3: proactive steps for your practice

The most effective AT3 prevention happens at intake, not at billing.

Build a relationship-verification step into your new patient workflow. Before any virtual encounter is booked for a patient you have not seen recently, check whether an in-person visit exists in your EMR within the past 24 months. This takes seconds and prevents the entire downstream problem.

Create a clear virtual-care eligibility protocol. Define internally which patient types require an in-person baseline before virtual billing begins. For new patients and anyone returning after a gap of two years or more, an in-person encounter should be the default first step.

Audit first-encounter documentation quality. We often under-document an initial visit because it feels routine, a brief intake note instead of a full assessment. If OHIP cannot read a complete clinical encounter in that note, the visit may not satisfy relationship verification. A five-minute documentation standard for first encounters pays back many times over in avoided rejections.

Train front-desk and admin staff on the 24-month rule. The physicians know the patients. The admin team manages the scheduling workflow. When admin staff understand why in-person bookings matter for billing eligibility, not just clinical preference, the protocol holds across the team.

Tracking these kinds of overhead costs matters more than most practices realize. The direct and indirect costs of managing AT3 rejections, including physician time reviewing charts, coordinating patient visits, and preparing resubmissions, can represent $26,000 to $39,000 in annual opportunity cost for a specialist practice running a typical billing volume.³

For a broader look at what billing errors cost over time, the true cost of DIY OHIP billing covers the compounding effect of rejection patterns most physicians never track.

AT3 and the broader OHIP rejection framework

AT3 does not exist in isolation. It belongs to a family of patient-relationship validation codes that work at different stages of adjudication:

AT3 (Error Report). Relationship not verified at validation. Claim rejected before processing.
B3 (Remittance Advice). Relationship requirements not met post-adjudication. Claim adjusted or denied on RA.
EH1 through EH6. A series of eligibility and enrolment codes that can intersect with relationship validation depending on the service type and specialty.

Understanding which stage your rejection is appearing at changes your response strategy. An Error Report rejection like AT3 needs a corrected resubmission. An RA-level explanation like B3 may require a different escalation path, including formal review.

OHIP's rejection code framework is intentionally complex. The prefix system alone (A-series for Error Report, V-series for validation, E-series for eligibility) requires familiarity most practices develop only through repeated exposure to rejections.¹ We have found that practices with professional billing support catch AT3 patterns across their entire billing history, not just on individual claims, which is the only way to see whether the root cause is systemic or situational.

For the full picture, how to read your OHIP remittance advice and what rejection codes actually mean is our field guide to the RA itself, and navigating OHIP rejections: a framework for Ontario specialist practices covers the diagnose, respond, and prevent workflow across all the common codes.

If you are evaluating which billing system or support model helps you stay ahead of codes like AT3, the ultimate guide to medical billing systems for Ontario physicians walks through the key decision factors.

Frequently asked questions

Does a telehealth visit count as a patient-physician relationship for OHIP?

A virtual visit alone does not establish a patient-physician relationship for future virtual billing. OHIP requires a physical in-person encounter within the past 24 months. You can bill a virtual service if an in-person encounter occurred within that window. Virtual and phone contacts do not reset or contribute to the 24-month clock on their own.

Can I resubmit an AT3 claim without the patient being seen in person again?

Only if you can document that the patient was seen in person within 24 months of the service date. If the relationship genuinely falls outside that window, you can resubmit with a manual review indicator and supporting clinical documentation explaining the circumstances. Resubmission without evidence will produce the same rejection. OHIP adjudicators need something to validate.

How long does the 24-month clock run?

From the service date backward. If you bill on June 15, 2026, OHIP looks for a physical encounter on or after June 15, 2024. Telemedicine, phone, and email contacts do not count toward the window. The clock restarts each time a qualifying in-person encounter is documented.

What counts as documentation that proves a patient-physician relationship exists?

A chart note from an in-person visit, such as a history and physical, a clinical assessment, or a consultation letter from a referring provider confirming the encounter occurred. Electronic medical record timestamps for phone or video calls alone are not sufficient. The note needs to reflect a face-to-face clinical encounter and be finalized with a clear date of service.

Is AT3 permanent, or can it be overturned on appeal?

AT3 is not permanent. If you have documentation of a qualifying in-person encounter within the 24-month window, file a corrected claim or a manual review request with that evidence. If the matter remains unresolved, you can escalate to the Health Services Appeal and Review Board (HSARB), which has authority to overturn AT3 rejections when documentation establishes that the patient-physician relationship existed. The key is having the chart evidence ready before you escalate.

If AT3 has appeared more than once in your recent remittance reports, there is a good chance it is part of a broader pattern in your billing history, one that is difficult to see when you are reviewing claims one at a time. If you would rather have someone handle the resubmission and follow-through for you, our Claims Concierge service manages that process end to end. If you are weighing up your billing setup more broadly, you can also book a free OHIP billing review.