Understanding Medicare’s 8-Minute Rule for Physical Therapy (and Related Therapy) Billing

(updated: 8/2026)

Medicare’s 8-minute rule is the longstanding methodology used by the Centers for Medicare & Medicaid Services (CMS) to determine how many units of time-based (constant-attendance) therapy services may be billed under Medicare Part B for outpatient physical therapy (PT), occupational therapy (OT), and speech-language pathology (SLP) services. The rule has been in effect since approximately 2000 and is codified primarily in the Medicare Claims Processing Manual, Chapter 5, Section 20. The core thresholds and calculation method have remained unchanged through 2025 and into 2026.

This article explains the rule completely and accurately, including how units are calculated, the distinction between timed and untimed codes, handling of multiple services, same-day evaluation and treatment, documentation requirements, common errors, differences from other payer rules, and practical compliance considerations. Always verify the most current guidance with your Medicare Administrative Contractor (MAC), as local coverage determinations or contractor interpretations may add nuance, and commercial payers often follow different standards.

What the 8-Minute Rule Is

The 8-minute rule governs billing for timed CPT codes that represent direct, one-on-one skilled therapy. These codes are defined in 15-minute increments. To bill any unit of a timed service, at least 8 minutes of skilled, face-to-face treatment must be provided. When multiple timed services occur on the same day for the same discipline, CMS requires aggregation of the total timed minutes to determine the maximum number of billable units.

The rule does not apply to untimed (service-based) codes. It applies to outpatient therapy services paid under the Medicare Physician Fee Schedule (or equivalent institutional rates) for Part B beneficiaries.

Key principle from CMS: Providers bill units based on the total minutes of timed services furnished on a single calendar day. The expectation is that each unit averages approximately 15 minutes of direct patient contact; consistent under- or over-billing relative to this average can invite review.

Timed vs. Untimed Codes

Timed (time-based / constant-attendance) codes require one-on-one skilled contact and are billed in units according to the 8-minute rule. Common examples include:

• 97110 Therapeutic procedure, one or more areas, each 15 minutes; therapeutic exercises
• 97112 Neuromuscular reeducation
• 97116 Gait training
• 97140 Manual therapy techniques
• 97530 Therapeutic activities
• 97035 Ultrasound (attended)
• Certain other modalities and procedures that specify timed, direct contact

Untimed (service-based) codes are billed as 1 unit per session regardless of duration. Minutes spent on these codes are excluded from the timed-minute total used for the 8-minute rule. Common examples include:

• Physical therapy evaluations (97161 low complexity, 97162 moderate, 97163 high complexity)
• PT re-evaluation (97164)
• Occupational therapy evaluations and re-evaluations (97165–97168)
• Supervised (unattended) modalities such as hot/cold packs (97010) or unattended electrical stimulation (97014 or G0283)
• Group therapy (97150) in many contexts

Only the minutes of skilled, one-on-one timed services count toward the 8-minute rule calculation. Do not add evaluation time, rest periods, unattended modalities, or documentation performed after the patient leaves to the timed total.

How Units Are Calculated – The Official Chart and Method

CMS instructs providers to total all minutes of timed services for the day (for that discipline) and apply the following ranges (Medicare Claims Processing Manual, Chapter 5):

Calculation steps:

1. Identify and sum only the minutes of skilled, one-on-one timed services provided on that date of service.
2. Determine the maximum number of units from the total using the chart above.
3. When multiple different timed codes were performed, allocate the units among the codes. Generally, assign more units to the service(s) with the greater number of minutes. If remainders from different codes combine to meet the 8-minute threshold for an additional unit, that unit is typically assigned to the code with the largest remainder (or greatest total time).
4. Do not bill any timed code for fewer than 8 minutes when it is the only timed service, or when the remainder after full units is fewer than 8 minutes.

Examples drawn from CMS guidance and standard application:

• Single service: 25 minutes of 97110 → 2 units.
• Multiple services: 20 minutes 97110 + 20 minutes 97140 = 40 total timed minutes → 3 units (e.g., 2 of one code and 1 of the other).
• 24 minutes 97112 + 23 minutes 97110 = 47 minutes → 3 units (typically 2 of the longer service and 1 of the other).
• 18 minutes 97110 + 13 minutes 97140 + 10 minutes 97116 + 8 minutes 97035 = 49 minutes → maximum 3 units (allocate to the services with the most minutes; the ultrasound may not receive a unit if minutes are insufficient after allocation).
• Seven minutes each of three different timed codes (total 21 minutes) → 1 unit, assigned to any of the codes (or the one with the most clinical emphasis).

If the total timed minutes are less than 8, no timed units may be billed.

Same-Day Evaluation and Treatment

CMS permits billing an evaluation (or re-evaluation) and timed treatment services on the same day when both are medically necessary. The evaluation is billed as 1 untimed unit. Its minutes are recorded as part of total treatment time but are not included in the Timed Code Treatment Minutes used for the 8-minute rule.

Documentation must clearly describe the treatment provided in addition to the evaluation. The claim and record must support that skilled timed interventions occurred separately from (or in addition to) the evaluative components.

There is no CMS rule that automatically caps timed units based on a scheduled appointment length (e.g., a 40-minute slot) or that treats evaluation time as subtracting from a fixed pool of available timed minutes. Actual session length is determined by medical necessity and the services furnished. If a thorough evaluation legitimately consumes significant time and only limited skilled timed treatment follows, bill only the units supported by the actual timed minutes. Extending the overall encounter or structuring care so that substantial timed skilled treatment is also delivered is permissible when clinically appropriate and fully documented. Billing timed units that were not furnished, or misrepresenting evaluation time as timed treatment, is improper.

Documentation Requirements

Per the Medicare Benefit Policy Manual, Chapter 15, Section 220.3 (and related Claims Processing Manual guidance):

• Treatment notes must document the total number of timed-code treatment minutes and the total treatment time (which includes timed + untimed services).
• The amount of time for each specific intervention is not required to be broken out in every treatment note, but the total timed minutes must support the units billed.
• Documentation must establish medical necessity, skilled care, the patient’s condition and response, and progress (or justification for maintenance therapy where applicable).
• Notes must be contemporaneous, legible, and sufficient to justify the services on review.
• Exact clock start and stop times for each individual timed intervention are not a universal CMS mandate in the treatment note. They are, however, a widely recommended best practice for audit defense because they eliminate ambiguity about duration.

Vague statements such as “exercises for 20 minutes” without supporting clinical detail or totals that match the claim create risk. The record as a whole must support every unit billed.

Assistant (PTA/OTA) Considerations

When services are furnished in whole or in part by a PTA or OTA, the CQ (PT) or CO (OT) modifier applies under the de minimis standard (generally when the assistant’s independent portion exceeds 10%). Specific exceptions involving the 8-minute rule exist for the final unit(s) in certain scenarios (detailed on the CMS Therapy Services page and in CY 2022 PFS final rule guidance). Payment for services with CQ/CO is reduced to 85% of the otherwise applicable amount. These rules interact with, but do not change, the underlying unit calculation for timed codes.

Differences from Commercial Payers and the AMA “Rule of Eights”

Many commercial and private payers follow the CPT/AMA midpoint or “Rule of Eights” / substantial-portion methodology, which applies the 8-minute threshold per individual code rather than aggregating total timed minutes across codes. Under that approach, remainders generally cannot be combined across different codes to create an extra unit. Some payers follow Medicare’s method; others have proprietary rules. Always check the specific payer’s policy. APTA recommends consistency where possible but notes the distinction.

Common Mistakes and Compliance Risks

• Including untimed evaluation or modality minutes in the timed total.
• Billing units for less than 8 minutes of timed service (or remainders under 8 minutes).
• Over-allocating units beyond the total supported by documented timed minutes.
• Failing to document total timed minutes and total treatment time.
• Billing timed codes for activities that were not skilled one-on-one interventions.
• Assuming a scheduled slot length creates a hard regulatory limit on units independent of actual services performed.
• Applying the Medicare aggregation method to payers that require the AMA per-code method (or vice versa).

Overbilling unsupported units, or under-documenting, can lead to denials, recoupments, or audits. Accurate contemporaneous documentation is the primary defense.

Status in 2025–2026

CMS made no changes to the 8-minute rule unit thresholds or core calculation methodology for 2025 or 2026. The rule remains as defined in the Medicare Claims Processing Manual, Chapter 5. Related policies that continue to apply include the KX modifier threshold (for therapy exceeding the annual amount, indexed annually), multiple procedure payment reduction (MPPR), therapy modifiers (GP/GO/GN), and assistant modifiers (CQ/CO). Documentation standards emphasizing medical necessity and support for timed minutes have been consistent requirements; increased audit focus on therapy claims is a recurring theme rather than a novel 2025 mandate tied specifically to new start/stop-time rules.

Practical Steps for Accurate Application

1. Record the services and the minutes of each timed intervention as they occur.
2. Sum only timed skilled minutes at the end of the encounter.
3. Apply the unit chart to the total.
4. Allocate units appropriately among the timed codes performed.
5. Ensure the treatment note contains the required total timed minutes, total treatment time, clinical description, and medical-necessity support.
6. Separate evaluation components clearly when billed on the same day.
7. Use software or checklists that enforce the aggregation method and flag mismatches between documented minutes and claimed units—but verify that any tool correctly implements CMS (not AMA) logic for Medicare claims.
8. Periodically audit a sample of claims against the record.
9. Consult your MAC’s local coverage articles and the current CMS Therapy Services resources for any contractor-specific expectations.

Conclusion

Medicare’s 8-minute rule is a straightforward total-time methodology for converting skilled timed therapy minutes into billable units. It requires at least 8 minutes for the first unit and follows 15-minute increments thereafter, with aggregation across timed codes on the same day. Untimed services such as evaluations are billed separately and their minutes are excluded from the calculation. Same-day evaluation and treatment are allowed when both are necessary and properly documented. The documentation must