If you’ve ever had a claim for a physical therapy re-evaluation denied or flagged for review, you’re not alone. It usually comes down to one small but critical piece of the billing puzzle: the modifier.
So let’s clear it up — what modifier do you use when billing for PT re-evaluation? And when is a modifier even necessary?
At PT Billing, we specialize in physical therapy revenue cycle management, and we see this issue trip up even experienced clinics. So we’re breaking it down here: no vague rules, no over-complication — just the facts that help you get paid.
First: When Is It Appropriate to Bill for a PT Re-Evaluation?
You can’t bill CPT code 97164 (PT re-evaluation) just because it’s been a few visits or a couple of weeks. According to CPT guidelines, a re-evaluation is only appropriate when there’s been:
- A significant change in the patient’s condition
- A need to update or modify the plan of care
- New clinical findings that require objective re-assessment
This is a distinct service, not routine documentation. If you’re billing 97164 without a clinical reason, payers will flag it — and often deny it.
So, Do You Need a Modifier for 97164?
Most of the time, you don’t. If 97164 is the only code you’re billing on that date of service, and it’s justified by your documentation, it typically doesn’t require a modifier.
But here’s where it gets more nuanced.
If the payer is Medicare — or if you’re billing multiple services on the same day — you may need to attach the right modifier to avoid bundling issues or compliance errors.
When You Do Need a Modifier for a PT Re-Evaluation
1. Billing to Medicare Part B? Use the GP Modifier
If you’re submitting claims to Medicare for physical therapy services — including re-evaluations — you must include modifier GP. This modifier tells Medicare that the service is part of a physical therapy plan of care.
Failing to include GP on 97164 will likely result in a denial. It’s a required modifier, even if it’s the only service you bill that day.
Bottom line: For Medicare, always attach GP to 97164.
2. Billing Multiple Services or a Separate Evaluation? Use Modifier 59
Let’s say you’re billing 97164 (re-evaluation) on the same day as another distinct, unrelated service — such as:
- An initial evaluation for a completely new condition or body part
- Manual therapy or modalities that typically bundle with the re-eval
In these cases, you’ll often need to attach modifier 59 to show that the re-evaluation was a separate and distinct service. This modifier prevents the payer from automatically bundling the services into one code — which means you’d get underpaid or denied.
Important: Modifier 59 should be supported with strong documentation. If you can’t show that the re-evaluation was independent of the other services, don’t use it.
Other Situations to Watch
Some payers — especially commercial ones — are transitioning away from modifier 59 in favor of more specific X modifiers (like XU for “unusual non-overlapping services”). But unless your payer specifically requires them, 59 and GP are still your most reliable options.
At PT Billing, we track these payer-specific rules and update modifier usage based on the most current guidelines — so our clients never get tripped up by shifting requirements.
Documentation Is Key — And So Is Strategy
Payers aren’t just looking for the right codes — they’re scanning claims for clinical justification. That means your re-evaluation note should clearly explain:
- What changed in the patient’s condition
- Why a new assessment was needed
- How the plan of care is being adjusted
Without that, even the right modifier won’t save you from a denial.
At PT Billing, we not only submit your claims — we audit your notes, flag potential modifier needs, and make sure everything lines up before submission. That’s how we keep re-eval claims clean, compliant, and paid.
Final Takeaway: Use the Right Modifier or Risk the Reimbursement
If you’re still asking “What modifier do I use when billing for PT re-evaluation?” — here’s the simplified answer:
- No modifier needed if you’re billing 97164 alone (non-Medicare)
- Use GP on all Medicare claims for PT services, including re-eval
- Use 59 when billing a separate and distinct evaluation or service on the same day
If in doubt, your best move is to clarify with the payer — or let a billing team (like us) handle it before mistakes cost you time and revenue.
Tired of Denials and Modifier Confusion?
We get it. Modifier errors don’t just lead to claim denials — they slow cash flow, create compliance risk, and frustrate your staff. That’s why PT Billing offers expert billing services built specifically for physical therapy clinics.From modifier logic and clean claims to compliance reviews and payer communication — we’ve got you. Contact us today to get your billing tight, your claims paid, and your team free to focus on care.