TK Modifier: Billing an Extra Passenger or Escort on a NEMT Trip

What the TK modifier means

CMS lists TK in the national HCPCS code set as “Extra patient or passenger, non-ambulance.” It has been in the code set since April 1, 2002. The October 2026 quarterly HCPCS file gives it coverage code I, which means Medicare does not pay it.

A modifier is a two-character tag on a billing code. It changes what the line pays for, not the code itself. TK goes on a base code, such as A0130 for a wheelchair van, and says the line is for a second person on the same trip. See NEMT billing codes for the base codes it goes with.

Because Medicare does not use TK, there is no national rule on who the extra person is. Each Medicaid program, and each health plan or broker paying under it, decides. In the programs below, TK marks one of these:

• A second Medicaid rider sharing the vehicle on the same trip.
• A companion or escort, such as a parent riding with a child.
• A second attendant, on top of the first one.
• A shared ride, which New York uses to bill a per-person surcharge.

Ambulance trips use a different modifier. GM means “Multiple patients on one ambulance trip.”

Which states use TK and what it pays

Program	TK goes on	What it marks	TK rate	Effective
South Dakota Medicaid	A0100, A0120, A0120 TN, A0130, and T2005 base codes, and its ambulance base codes too	An additional South Dakota Medicaid recipient	50 percent of the base: $2.60 taxi or in-town mini-bus, $3.90 mini-bus outside the city, $21.70 secure van, $54.83 stretcher van	July 1, 2026
Indiana Medicaid	A0130, and A0100 with UA, UB, or UC	An accompanying adult or attendant	$15.90 on a wheelchair van. On a taxi, $3.81, $6.36, or $9.54 by distance.	January 1, 2026
Illinois Medicaid	T2001	An additional attendant	$20.00 on service car and medicar (wheelchair van) trips, $0.46 on taxi trips	January 1, 2026. The TK line dates from October 1, 2013.
Alaska Medicaid	A0100, A0120, and air codes	An escort	Billed charges. A member and escort riding together cannot be billed more than the total fare.	July 1, 2026 to June 30, 2027
New York Medicaid	A0170	A pool trip, for the New York City congestion surcharge on taxi, livery, and rideshare trips (ambulettes are exempt)	$0.75 per person. A single-rider trip bills TU at $2.75.	Surcharge since January 1, 2019. Policy manual effective August 25, 2023.

If your state’s fee schedule has no TK line, do not add one. A modifier your payer does not accept on that code can deny the line. On a remittance, that can show up as adjustment reason code 4, “The procedure code is inconsistent with the modifier used.”

TK on a shared ride: the South Dakota example

South Dakota’s modifier list, effective July 1, 2026, sets TK at 50 percent of the established fee. Its community and secure transportation manuals, updated August 2026, define TK as an additional South Dakota Medicaid recipient. Both manuals allow only one mileage allowance per trip, however many riders are on board, billed on one rider’s claim. Secure van mileage is paid only outside city limits, counted from the point the trip leaves them.

Example. A secure van takes two Medicaid members from the same town to the same clinic, 20 loaded miles counted from the city limits. Each member gets their own claim.

Claim	Code	Units	Amount
First member, base	A0130	1	$43.39
First member, mileage	S0209	20	$52.20
Second member, base	A0130 TK	1	$21.70
Second member, mileage	None	0	$0.00
Total			$117.29

The same two members on separate trips would pay $191.18. The shared ride pays less in total but uses one vehicle, one driver, and one set of miles. See NEMT multiloading for planning shared rides.

TK for escorts and attendants

Indiana. The transportation module (version 6.1, published August 19, 2025) says members younger than 16 must have an adult with them, and adult members may need an attendant for medical reasons. You bill the base code and the companion’s code together, both under the member’s Medicaid ID:

Type of ride	Base code	Companion code
Walk-on (commercial ambulatory)	T2003	T2001
Wheelchair van (nonambulatory)	A0130	A0130 TK
Taxi, 0 to 5 miles	A0100 UA	A0100 UA TK
Taxi, 6 to 10 miles	A0100 UB	A0100 UB TK
Taxi, 11 miles or more	A0100 UC	A0100 UC TK

Two conditions apply. Indiana pays nothing extra for a companion if you do not charge your other customers for one. And the driver’s ticket must show the companion’s name, signature, and relationship to the member.

Illinois. TK goes on T2001, the attendant code, to bill a second attendant. The handbook (March 11, 2024) makes every attendant subject to prior approval. A medicar may bill both an employee and a non-employee attendant on one trip, while a service car or taxi is paid only for a non-employee attendant. Passengers who are not approved attendants ride free as a courtesy.

Alaska. The state fiscal year 2027 schedule uses TK to mark an escort on taxi, other ground travel such as train or ferry, and air lines, paid at billed charges. A taxi claim over $89 needs a copy of the travel voucher and the charge slip.

When a second rider is billed without TK

Many programs mark a shared ride another way:

• Indiana: a second or later member carried from the same county to the same area pays half the base rate, with no mileage or waiting time. Walk-on extras bill T2004, and wheelchair extras bill A0130 TT, $15.90 as of January 1, 2026.
• Medi-Cal: a lower wheelchair van base for each rider, set by the number of patients: $16.22 each for two (UN), $12.85 for three (UP), and $11.51 for four or more (UQ, UR, or US). The rate page was updated September 2023.
• Illinois: a separate claim for each rider, each with a full base rate. Only the first rider picked up gets mileage, on the direct route for that rider.
• Arizona: a separate daily trip report for each member, with the miles of that member’s most direct route. Waiting time is paid for one member only (Chapter 14, revised July 31, 2026).

Broker trips follow the broker’s rate sheet. MTM Health’s Virginia handbook (approved August 10, 2026) says its payment reflects mileage, mode of transportation, and multiloading opportunities.

How to bill TK without a denial

1. Find the TK line. Look for your base code with TK on your state’s fee schedule or your broker’s rate sheet.
2. Know who it pays for. South Dakota means another Medicaid rider. Indiana means a companion. Illinois means a second attendant.
3. Put it on the right claim. In South Dakota the extra rider’s own claim carries TK. In Indiana the companion’s line goes on the member’s claim.
4. Bill mileage once where your program says so, as South Dakota and Illinois do.
5. Keep the modifier order your payer shows, such as A0100 UA TK. Box 24D of the CMS-1500 holds up to four modifiers per line. See the CMS-1500 for NEMT and origin and destination modifiers.
6. Record the extra person on the trip record: name, relationship, and signature where required, plus the approval number for any attendant.