March 2024, third week. I’m reviewing claims data for a PT clinic in Woodbridge, New Jersey and something doesn’t smell right. On Tuesday afternoon, their therapist recorded 22 minutes of therapeutic exercise (97110) and 20 minutes of manual therapy (97140) for a patient. Total treatment time: 42 min. The biller billed 3 units for the 97110 and 2 units for the 97140. Five units in total.
Should have been four.
The biller was rounding each code separately, instead of totaling the minutes of treatment and then dividing out units. That one mistake, multiplied by 14 patients a day, five days a week, had quietly overbilled Medicare for almost two months. So when I ran the numbers the clinic was up-coding about $4,300 worth of claims that were technically fraudulent under CMS rules. Not on purpose. Not because of. Because nobody explained to the biller how the 8-minute rule actually worked.
And here’s what annoys me. The biller had been around. She had been coding PT claims for 6 years. 6 years of doing it wrong.
So What Exactly Is the 8-Minute Rule Then?
Every time a physical therapist performs a timed service (therapeutic exercise, manual therapy, neuromuscular re-education, gait training to name a few) Medicare wants to know how many 15 minute units you are billing. That makes sense. But the question no one asks until it bites them is: what happens when the treatment time isn’t evenly divisible by 15 minute blocks?
That’s where the 8-minute rule comes in. And despite the name, it has nothing to do with treating patients for 8 minutes.
The rule says this: you must have at least 8 minutes of a timed service to bill one unit. Anything less than 8 minutes? No, you can’t bill that at all. Nothing. Poof. Does not count. Between 8 and 22 minutes you receive one unit. You don’t get a second unit until you hit the 23 minute mark. The whole system is based on total combined minutes across all the timed codes performed during the session not per individual code.
Most people don’t get that last bit right. And I will say it again because it is important: you calculate billable units based on the TOTAL timed minutes for the ENTIRE visit and then allocate those units to the codes you used. Not code after code.
My Cheat Sheet Stuck to My Computer Screen
I’ve had this table up since back when I was annoyed that I had to calculate things mentally whenever someone wanted to know how many units there were. This cheat sheet still sits on my computer screen stuck to it with a sticky note.
| Total Timed Minutes | Billable Units | Remaining Minutes |
| 8 to 22 minutes | 1 unit | Up to 7 min unused |
| 23 to 37 minutes | 2 units | Up to 7 min unused |
| 38 to 52 minutes | 3 units | Up to 7 min unused |
| 53 to 67 minutes | 4 units | Up to 7 min unused |
| 68 to 82 minutes | 5 units | Up to 7 min unused |
| 83 to 97 minutes | 6 units | Up to 7 min unused |
Practical Example (As The Theory Will Be Worthless Otherwise)
Wednesday afternoon. Your physical therapist treats a patient who recently had a total knee replacement surgery. He logs his minutes as follows:
Therapeutic exercises (97110): 18 minutes. Manual therapy (97140): 15 minutes. Neuromuscular re-education (97112): 12 minutes.
Total timed minutes: 45.
Check the table. 45 is within the range of 38 to 52 minutes. That means 3 units of time billing.
Then allocate 3 units among the codes in question, prioritizing the codes based on how many minutes they took. 97110 would get 1 unit (18 min); 97140 – 1 unit (15 min); 97112 – 1 unit (12 min). 3 units allotted to 3 codes. Task accomplished.
The mistake your biller should not make: calculate units of time for each code separately. If that was the way, your biller would say 1 unit for 18 minutes of 97110; 1 unit for 15 minutes of 97140; 1 unit for 12 minutes of 97112. Same result. However, shift the minutes in any direction and you will have the independent method yielding false results. Sometimes too low. Sometimes too high.
The Mistakes I See Over and Over (And They’re Always the Same Ones)
Having audited physical therapy coding and billing at clinics in New Jersey and New York over the last 3 years, I would say that about 80% of the clinics that I have examined commit the same mistakes over and over again. I’m getting bored already!
Mistake #1: Rounding Individual Codes
I’ve already addressed this particular mistake in the case of the Woodbridge clinic. The clinic bills individual codes separately, without adding up total minutes for treatment. As I already mentioned, Medicare has stated explicitly that total treatment time dictates the number of units, which cannot be calculated separately per each individual code.
Mistake #2: Billing a Unit of Therapy for 7 Minutes
I recall a case when a physical therapist from a clinic located in Edison had performed gait training (CPT code 97116) for 7 minutes at the end of a session. However, the biller decided to bill it as 1 unit of therapy. Absolutely incorrect! 7 minutes does not meet the minimum of 8 minutes required by Medicare. It cannot be billed at all since it doesn’t exist from a billing perspective.
Mistake #3: Forgetting to Not Include Untimed Codes
The seasoned billers make this mistake too. Some CPT codes in physical therapy services are untimed, meaning they cannot be counted based on time duration. This list includes hot packs (97010), electrical stimulation (unattended) – either code 97014 or G0283 when billing to Medicare, and evaluations (97161 to 97163). Untimed codes have to be billed in 1 unit no matter what. The 8-minute rule does not apply to them; however, I have seen billers include hot pack time while calculating total timed minutes. Overbilling can get you into serious trouble – especially with Medicare.
Mistake #4: Uncertain Timing in Notes
“When the patient performed therapeutic exercise, it lasted for about 20 minutes.” When it comes to documentation of therapy time, the “about” phrase gets you into trouble. In case of CMS audit, the agency wants you to be very accurate in terms of timing, so using phrases like “approximately” or “about” makes the documentation incorrect. I always advise the clinics I work with to use numbers.
Mistake #5: Failing to Remember the Rule Applies to Commercial Carriers as Well
The 8-minute rule is actually a Medicare or CMS rule. However, here’s where confusion sets in: many private payers such as Blue Cross, Aetna, United Healthcare, and Cigna have copied the CMS rule in their guidelines or even come up with something very similar to the CMS rule. Some have even opted to use the AMA’s timed code method instead, which calculates coding units differently from that of the CMS rule. You may find yourself over-billing or under-billing commercial claims because of this.
Why Getting This Wrong Costs You Actual Money
Let me put real dollars on this because I think abstract rules don’t motivate people the way dollar signs do.
One unit of 97110 reimburses approximately $34 to $36 under the 2026 Medicare fee schedule. If your biller undercodes by just one unit per patient and you see 25 Medicare patients a day, that’s roughly $850 in lost revenue. Per day. Multiply by 20 working days and you’re looking at $17,000 per month sitting on the table because someone calculated units wrong.
Flip it around. Overbilling by one unit per patient exposes you to Medicare audits, post-payment clawbacks, and potential fraud allegations. Claim denials from unit miscalculations accounted for nearly 20% of PT claim rejections in recent CMS data. That’s not a rounding error. That’s a systemic problem hitting clinics nationwide.
Either direction, wrong unit counts cost you. Underbilling means you’re working for free. Overbilling means you’re working toward an audit. Neither is acceptable.
Quick Guide: Which PT Codes Are Timed and Untimed
I get this question all the time so here it is all in one piece.
Timed codes (8-minute rule applies):
97110 Therapeutic exercise. 97112 Neuromuscular re-education. 97116 Gait training. 97140 Manual therapy. 97530 Therapeutic activities. 97535 Self-care/home management training. 97542 Wheelchair management training. 97750 Physical performance test.
Untimed codes (charge only once per visit regardless of time spent):
97010 Hot/Cold Packs. 97014 Unattended electrical stimulation. G0283 Medicare electrical stimulation. 97161/97162/97163 PT evaluation. 97164 Reevaluation of the patient by a physical therapist. 97150 Group Physical Therapy treatment.
When you have an untimed code, do not count the minutes from that code when doing your timed code distribution. If the code is timed, all minutes are relevant to unit distribution calculations
Why It Is Important for Your Partner to Understand This
This is where I want to make this point relevant to what you do for a living since it makes no difference whether you know about the 8-minute rule and apply it in all your cases, or whether you understand this principle and are able to calculate your units accordingly.
Therapists who work with your patients are busy treating their patients; they take time to document in between visits or maybe even during the lunch break or at night. You should not expect them to focus on calculating their units properly while also doing their documentation. If, however, your billing partner calculates everything but doesn’t stay up-to-date with changes introduced by payers regarding this rule, you face a situation that leads to denied claims or audits.
That’s where an expert physical therapy billing firm really pays off tenfold. A group that processes only PT claims knows the 8-minute rule chart by heart. They notice when there’s a 7-minute gait training procedure being documented and mark it as an invalid time frame for billing. They are aware of a therapist who always uses “approximately 20 minutes” and offer the correct wording. They have knowledge about which private insurance companies adhere to the CMS guidelines and which ones use the AMA time billing process. That level of experience dealing with physical therapy billing is very difficult for an individual biller to achieve.
Park Medical Billing handles this level of detail as a core part of their operation. Their team works through unit calculations, modifier sequencing, and Medicare compliance requirements with the kind of automatic precision that comes from specializing in PT billing for over a decade. They resolve most claim denials in 7 to 14 business days, and their clients regularly report up to 20% revenue growth within six months of partnering together. That kind of lift usually starts with exactly the stuff we talked about in this blog: getting the unit counts right, cleaning up documentation language, and eliminating the small coding mistakes that bleed revenue quietly.
What sold me on recommending them was the reporting. Park builds custom financial reports for each practice. Reimbursements by payer. Collections by CPT code combination. Provider performance tracked individually. That’s the kind of visibility that lets a clinic owner spot an 8-minute rule problem before it turns into a five-figure audit liability.
Founded by Chol Park, headquartered in Englewood, New Jersey, with a BBB A+ rating, Park Medical Billing works with physical therapy practice owners in NJ, NY, and across the country. If your clinic is still relying on sticky notes and mental math to calculate timed units, that’s a fixable problem. Park offers a free consultation where they’ll review your billing patterns and show you exactly where revenue is slipping through. No commitment, no pressure. Just a clear look at your numbers from people who calculate PT units in their sleep.
FAQ Questions About PT Billing Rules
1. Is the 8-minute rule for all insurance plans or just Medicare?
Strictly speaking, the 8-minute rule is a CMS/Medicare rule. However, most commercial payers such as Blue Cross, Aetna, and UnitedHealthcare use rules similar to this one. Some commercial insurance companies adopt the AMA’s Direct Time Method that calculates units in a little different way. It is best to look up each payer’s policy regarding timed codes rather than assume that all insurance plans follow the CMS rule. A specialized PT billing company monitors these variations on a daily basis.
2. What should I do when my therapist spends 7 minutes on a timed procedure?
According to the 8-minute rule, you can only bill for a separate unit when spending at least 8 minutes on one timed procedure. Thus, the 7 minutes will be counted as a contribution to your overall timed minutes in the session. Once added to the other timed procedures’ minutes, these minutes might make you go over the next 15 minutes mark (37 – 44 minutes, for example).
3. What happens when there are timed and untimed codes on the same visit?
It is essential to keep them separate. The untimed codes include hot packs (97010) and unattended e-stim (97014/G0283) that can be billed once per session independent of the treatment duration. It is important not to confuse them since their time is NOT included in the overall time. Only the timed CPT codes, including 97110, 97140, 97112, and 97530 should be used to calculate 8-minute rule.
4. If my treatment lasts for 16 minutes can I code 2 units?
No, two units are allowable starting from 23 minutes. The additional unit starts counting once there are at least 8 minutes in the second 15 minutes (15+8=23). This is the formula that most often gets mixed up by billers.
5. How does CMS 8-minute rule differ from AMA rules?
Under CMS 8-minute rule, one needs a minimum of 8 minutes within any 15-minute interval to bill an extra unit, and calculation is done using the total number of minutes of timed activities. In the case of AMA direct time calculation method, each 15-minute unit can be charged when one spends “a majority” of 15 minutes per unit, that is, 8 minutes per each code. The main difference between the two occurs when one works for short intervals on several codes. CMS combines everything while AMA calculates for each code separately.
