Coding for Time-Based Services: Common Mistakes & How to Justify Time-Driven CPT Codes

In the evolving world of medical billing and coding, time-based services present a unique challenge. Unlike procedure-based billing, where the focus is on what was done, time-based CPT coding centers around how long a service was performed or how much time was spent with the patient. This method is most commonly applied in services such as psychotherapy, evaluation and management (E/M), prolonged services, critical care, and physical therapy.

However, coding for time-based services is often misunderstood and misapplied, leading to reimbursement denials, compliance issues, and even audit risks. This blog explores the fundamentals of time-based CPT coding, common mistakes practices make, and strategies to justify time-based codes for clean claim submission and maximum reimbursement.

Understanding Time-Based CPT Codes

Time-based CPT codes are billed based on the amount of time a healthcare provider spends directly performing a service. These codes are especially relevant when:

Time is explicitly listed in the CPT code description.
Time dictates the level of service provided (e.g., psychotherapy, prolonged services).
The code requires documentation of start and stop times, or total face-to-face time.

Key Examples Include:

Psychiatry (90834, 90837) — Based on the length of the session.
Prolonged Services (99417, 99358) — Additional time beyond primary E/M service.
Critical Care (99291, 99292) — Based on time spent actively managing a critically ill patient.
E/M Services (2021 Guidelines) — Time may be used to select code level when appropriate.

Common Mistakes in Time-Based Coding

1.Failing to Document Total Time

Many providers mistakenly bill time-based codes without clearly documenting total time spent, or by only noting vague phrases like “lengthy visit” or “extended time.” Without time documentation, the payer cannot validate the claim.

Best Practice: Always include either:

Total time (e.g., “Total time: 50 minutes”)
Start and stop time (e.g., “Start: 3:05 PM, End: 3:55 PM”)

2.Mixing Face-to-Face and Non-Face-to-Face Time Incorrectly

Certain codes allow inclusion of non-face-to-face time (e.g., care coordination), while others only count direct patient interaction. Including the wrong type of time can lead to overcoding or denials.

Example: For outpatient E/M visits, only total time on the date of service is counted. Activities before or after that date do not apply.

3.Overlooking CPT Time Thresholds

Every time-based CPT code has a minimum time requirement. Providers sometimes bill for a service without meeting the threshold time, such as billing CPT 90837 (60-minute psychotherapy) when only 40 minutes were spent.

Rule of Thumb: At least midpoint of the stated time must typically be met to justify the code (also known as the 8-minute rule in some scenarios).

4.Using Time When Medical Decision-Making (MDM) Is More Appropriate

While time is a valid component for selecting E/M levels, some providers inappropriately use it when MDM would better support a higher-level code.

Tip: Use time-based coding only if:

Counseling and coordination dominate the encounter.
Total time spent is accurately documented.
Time thresholds meet or exceed requirements for higher code levels.

5.Incorrect Use of Prolonged Services Codes

Prolonged services codes (99417, 99358, etc.) are often misapplied, either added to E/M codes that don’t qualify, or without calculating time correctly.

Key Compliance Point:

CPT 99417 can only be used in conjunction with 99205 or 99215, and only after a full 15 minutes beyond the base time has been met.

How to Justify Time-Based CPT Codes Properly

✅ 1. Document Clearly and Quantitatively

The best justification is a well-documented record that includes:

Start and end times
Total time
Description of activities during that time

Example:
“40-minute session included medication review, behavioral counseling, and coordination with patient’s family regarding treatment plan.”

✅ 2. Align Time with CPT Descriptions

Match your documented time directly with the CPT code’s stated duration. For example, CPT 90834 is for 45 minutes of psychotherapy; do not bill this code unless that duration (or close to it) was met and recorded.

✅ 3. Include the Time on the Claim Form (When Applicable)

When submitting claims, some payers allow or require that time be indicated in the notes field or within an electronic submission format. Work with your billing team or vendor to ensure this is submitted when applicable.

✅ 4. Train Providers on Documentation Standards

Educate physicians and mid-level providers about:

Which codes are time-based
Time thresholds
Proper ways to document time

Consider creating EMR templates that guide providers to include required fields for time-based codes.

✅ 5. Monitor and Audit Time-Based Claims

Routinely review your claims data for trends such as:

Overuse of highest-level time-based codes
Prolonged service billing spikes
Patterns across providers

Regular auditing helps you spot compliance risks and ensure coding consistency.

Special Considerations by Service Type

Psychiatry and Mental Health

Codes like 90832, 90834, and 90837 are time-specific.
Documentation should include session focus, therapeutic techniques, and time.

Critical Care

CPT 99291 (first 30-74 mins) and 99292 (each additional 30 mins)
Must document both the medical necessity and the total time.

Telehealth

Use of time-based coding expanded under telehealth.
Ensure you’re capturing time correctly for audio-only vs. video visits.

Conclusion

Time-based CPT coding is a powerful tool when used correctly. It enables fair compensation for services that require substantial provider time and effort, particularly in behavioral health, E/M services, and critical care. However, it demands a high level of precision in documentation and coding strategy.

By avoiding common mistakes—like failing to document time, misapplying prolonged service codes, or confusing direct and indirect time—practices can boost reimbursements, stay compliant, and reduce denial rates. Educating your providers, using supportive EMR templates, and auditing for consistency are crucial steps in mastering time-based billing.

Ultimately, time-based coding isn’t just about counting minutes — it’s about telling the full story of patient care in a way that justifies the value of the service provided.