The ICU: Navigating the Complexities of Critical Care Billing

As an Ontario critical care physician, your focus is on stabilizing the sickest patients in the hospital, but accurate billing is what keeps your practice running smoothly. From ICU per diem codes to life-threatening critical care and resuscitative services, the array of OHIP billing codes and regulations can feel overwhelming. Getting them right is essential to being properly compensated for the crucial work you do every day.

In this blog post, we’ll dive into some key billing concepts every ICU physician should know to help you avoid missed billing opportunities and maximize your OHIP revenue.

What are the ICU per diem codes?

The Schedule of Benefits divides ICU per diem care into three types: Critical Care, Ventilatory Support and Comprehensive Care. The right code depends on two things: which aspects of the patient’s care you’re responsible for, and how many days the patient has been receiving that care.

Each type has a first-day fee, a per diem fee for days 2 to 30, and a lower per diem fee from day 31 onwards.

OHIP Critical Care Per Diem Codes (G400, G401, G402)

Critical Care applies when you’re providing all aspects of care for a critically ill patient in the ICU, except for ventilatory support. This includes:

• Initial consultation and assessment
• Emergency resuscitation
• Intravenous lines, cutdowns, intraosseous infusion, pressure infusion sets and pharmacological agents
• Insertion of arterial, C.V.P. or urinary catheters, and nasogastric intubation (with or without anaesthesia)
• Securing and interpreting laboratory tests, oximetry and transcutaneous blood gases
• Intracranial pressure monitoring interpretation and assessment when indicated (insertion of the I.C.P. measuring device is not included)

The billing codes for Critical Care are:

• G400: 1st day ($223.10)
• G401: 2nd to 30th day, inclusive, per diem ($146.45)
• G402: 31st day onwards, per diem ($58.60)

OHIP Ventilatory Support Per Diem Codes (G405, G406, G407)

Ventilatory Support applies when you’re providing ventilatory care for the patient. This includes:

• Initial consultation and assessment
• Intravenous lines
• Endotracheal intubation with positive pressure ventilation, including insertion of arterial and C.V.P. lines
• Tracheal toilet
• Use of an artificial ventilator and all necessary measures for its supervision
• Obtaining and interpreting blood gases, oximetry, transcutaneous blood gases and assessment

The billing codes for Ventilatory Support are:

• G405: 1st day ($183.80)
• G406: 2nd to 30th day, inclusive, per diem ($96.45)
• G407: 31st day onwards, per diem ($64.20)

OHIP Comprehensive Care Per Diem Codes for ICU Physicians (G557, G558, G559)

Comprehensive Care applies when you, as the Intensive Care physician, are providing complete care for the patient, meaning both Critical Care and Ventilatory Support. Along with the services listed above, it also includes subsequent examinations of the patient, defibrillation, cardioversion and usual resuscitative measures.

The billing codes for Comprehensive Care are:

• G557: 1st day ($429.30)
• G558: 2nd to 30th day, inclusive, per diem ($256.25)
• G559: 31st day onwards, per diem ($122.80)

ICU per diem codes at a glance

Fees are based on the OHIP Schedule of Benefits effective April 1, 2026.

Key rules to keep in mind

The Schedule of Benefits sets out several rules for billing ICU per diem codes. Here’s what you need to know:

• Team fees: Per diem fees apply per patient, not per physician. If the physician-in-charge changes, continue the day count. For example, bill G401, not G400, if you take over on day four.
• No other critical care codes: When you bill per diem codes, no other critical care codes can be paid to you for that patient.
• Ventilatory support by another physician: If a physician (such as an anaesthesiologist) provides only ventilatory support, they bill G405 to G407, and Comprehensive Care doesn’t apply. Other physicians bill Critical Care or consultation, visit and procedure codes.
• Other physicians: Can bill consultation, visit and procedure codes not included in the critical care fees. These claims are reviewed by the Medical Consultant on an Independent Consideration basis.
• Stabilized or monitored patients: Per diem fees can’t be billed unless the patient is on a ventilator. Bill consultation, assessment and procedure codes instead, as you would once per diem care has stopped.
• Transfers: The day of transfer counts as the second day of the new type of care (G401, G406 or G558), not the first.
• Re-admissions: The first-day rate applies again only if the patient was discharged from the unit for more than 48 hours.

Example

Let’s look at a common ICU scenario to see how these rules apply:

A patient is admitted to the ICU with septic shock, and you take over their care as the physician-in-charge. Here is the billing breakdown:

Day 1:

• Situation: Patient admitted to the ICU, not ventilated
• Billing: Critical Care, 1st day (G400)

Day 2:

• Situation: Ongoing critical care, still not ventilated
• Billing: Critical Care per diem (G401)

Day 3:

• Situation: Patient deteriorates and is intubated. You are now providing both critical care and ventilatory support
• Billing: Comprehensive Care per diem (G558)

Because the patient was transferred from Critical Care to Comprehensive Care, day three is billed as G558, not G557. Clear documentation of when the patient was intubated and when the type of care changed will help support your claim.

What are life-threatening critical care and resuscitative care? 

Life-threatening critical care and resuscitative care are two categories of critical care services provided in emergency situations. 

Life-threatening critical care is provided when a patient is critically ill or injured, with acute impairment of one or more vital organ systems leading to organ failure. The billing codes for this care include: 

• G521: First 15 minutes  

• G523: Second 15 minutes 

• G522: Additional 15-minute intervals (up to 6 units) 

Note: Up to three physicians can bill G521 for the same patient on the same day. 

Resuscitative care applies to emergencies that don’t meet the criteria for life-threatening critical care but still involve a potential threat to life or a high likelihood of the patient suffering limb loss or requiring life-threatening critical care. care. The billing codes for resuscitative care are: 

• G395: First 15 minutes 
• G391: Additional 15-minute intervals (up to 9 units) 

Critical care premiums

When a physician provides critical care services (when a patient is critically ill or injured, with acute impairment of one or more vital organ systems leading to organ failure) outside of regular hours, they may be eligible for additional compensation through premium codes. These premiums apply to critical care performed during specific time periods, billed alongside other non-assessment codes: 

Night Premium (H112): 

• Applicable hours: midnight to 8:00 AM.

• Can be billed in addition to regular critical care codes. 

Weekend and Holiday Premium (H113): 

• Applicable hours: 8:00 AM to midnight. 

• Covers critical care services provided on weekends and designated holidays. 

Note: These premiums can also be used for K623 (Form 1 psychiatric assessment) and K015 (Counselling of relatives on behalf of a terminally ill patient).

These premium codes allow physicians to receive extra compensation for providing critical care during less desirable hours or on days when most people are off work. They are added on top of the standard critical care billing codes to reflect the additional burden of working during these times.

Common billing errors related to critical care

Claims can be rejected for many reasons. The most common errors physicians see are M4 errors, which come back if the maximums have been exceeded. 

A few other common errors that physicians see are: 

• SX – ICU code already claimed by another physician. This error means the ICU code billed has already been claimed by another physician. It’s commonly seen with G600 and G400, and the Ministry will only pay these to one doctor per day. The fix is for the physician who received the error to rebill with G521, using units that reflect the exact time spent with the patient.
• D7 – Not allowed in addition to other procedure. Critical care team fees can’t be billed with a number of other codes, because they already include assessments and many other elements of care. Billing G400 alongside codes that aren’t allowed with assessments results in D7 rejections.

• VJ7 – Stale dated claim. This error occurs for two reasons: when the claim has been submitted past the 3-month billing deadline, or if the claim has been submitted on time but it hasn’t been corrected within 3 months. If the reason for missing the deadline is that the Ministry asked you for documentation and, by the time you gathered it and resubmitted, you missed the deadline, then documentation must be submitted for payment of the claim. Other than that, unless the circumstance for submitting a claim past the deadline is extenuating, the claim must be written off.

Conclusion

For Ontario critical care physicians, billing accurately is part of running a sustainable practice, alongside the clinical expertise you bring to every critically ill patient. Whether you’re a seasoned intensive care physician or just starting out, this guide covers the often-overlooked details of critical care billing, with real-world examples that can make a meaningful difference to your practice. 

With a firm handle on these practices, you can make sure you’re fully compensated for the work you do when your patients need you most. 

Last updated: October 2026. Codes and rules are based on the current OHIP Schedule of Benefits and may change. Always confirm with the Schedule of Benefits or contact our team.

Related Resources

We have related resources to help doctors navigate the complexities of critical care billing: 

ER Billing Codes Cheat Sheet

ER Special Premiums Quick Reference Guide

ER Billing Frequently Asked Questions

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