HCPCS Level II modifier
Modifier AT
Modifier AT is a HCPCS Level II modifier. CMS describes it as: Acute treatment (this modifier should be used when reporting service 98940, 98941, 98942).
Source: CMS HCPCS Level II, October 2026 file dated September 23, 2026. Publisher page
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- Modifier
- AT
- Type
- HCPCS Level II modifier, maintained by CMS
- CMS description
- Acute treatment (this modifier should be used when reporting service 98940, 98941, 98942)
- Claim form
- CMS-1500 item 24D, up to four modifiers per line. 837P SV101-3 to SV101-6.
- Guidance
- CMS HCPCS quarterly update
Related modifiers
- AUItem furnished in conjunction with a urological, ostomy, or tracheostomy supply
- ASPhysician assistant, nurse practitioner, or clinical nurse specialist services for assistant at surgery
- AVItem furnished in conjunction with a prosthetic device, prosthetic or orthotic
- ARPhysician provider services in a physician scarcity area
- AWItem furnished in conjunction with a surgical dressing
- AQPhysician providing a service in an unlisted health professional shortage area (HPSA)
- AXItem furnished in conjunction with dialysis services
- APDetermination of refractive state was not performed in the course of diagnostic ophthalmological examination
Related pages
Questions
What does modifier AT mean?
Modifier AT is a HCPCS Level II modifier. CMS describes it as: Acute treatment (this modifier should be used when reporting service 98940, 98941, 98942).
Is modifier AT a CPT or a HCPCS modifier?
AT is a HCPCS Level II modifier from the CMS quarterly HCPCS file. Two-digit numeric modifiers, such as 25 or 59, are CPT modifiers.
Where does modifier AT go on a claim?
On the CMS-1500 it goes in item 24D next to the procedure code. Each line holds up to four modifiers. On an 837P it goes in SV101-3 to SV101-6.
What denial comes back when a modifier is wrong?
A missing or mismatched modifier often comes back as CARC 4. A modifier that was not valid on the date of service comes back as CARC 182. A bundling edit the modifier should have bypassed comes back as CARC 97 or 236.