What does the TK modifier mean on a transportation claim?

TK in the national code set

TK is a two-character HCPCS modifier with the official descriptor “Extra patient or passenger, non-ambulance.” It dates from April 1, 2002, and CMS’s October 2026 file lists it with coverage code I, not payable by Medicare. Like any modifier, TK leaves the base code alone and adds a fact about the service: someone besides the primary rider was carried on that trip.

The descriptor never says who that someone is, so the payer decides, and the decision sets the price. On a paper claim, TK sits in box 24D beside the base code. Each line there takes as many as four modifiers.

Three ways programs pay a TK line

A share of the base rate

South Dakota prices a TK line at half of the established fee, and its fee schedule labels every TK line “Additional recipient.” The July 1, 2026 schedule spells out the math:

South Dakota pays a trip’s mileage once, no matter how many people ride. The second rider adds a base amount and nothing for miles.

A flat amount for someone riding along

Indiana treats TK as the companion line. The state requires an adult to travel with any member under 16, and it allows an attendant for an adult member whose medical needs require one. The companion goes on the member’s own claim, under the member’s Medicaid ID: A0130 TK on a wheelchair van, or A0100 with its distance modifier plus TK on a taxi. Commercial ambulatory (seated) trips bill T2001 for the companion instead.

An example: a wheelchair van carries a child and a parent eight miles to a clinic. Indiana adds van mileage only when the one-way distance tops 10 miles, so the claim is A0130 at $31.79 plus A0130 TK at $15.90, a total of $47.69 at the rates Indiana has paid since January 1, 2026.

Indiana adds two conditions. No companion payment is due when the provider does not charge its other customers for a companion. And the companion signs the driver’s ticket, which also records the companion’s name and how they are related to the member.

Illinois puts TK on T2001, its attendant code, to pay for a second attendant. Under the schedule effective January 1, 2026, T2001 TK is worth $20.00 on a service car or medicar and $0.46 in a taxi. Every attendant, employee or not, needs prior approval. One medicar trip can carry both an employee attendant and a non-employee attendant, such as a relative, and bill for each. Service cars and taxis are paid only for the non-employee kind. Other passengers may come along, but the handbook bars any extra charge for them.

A head count in the units field

Colorado replaced its old local mobility van codes, X6022 to X6030, with A0120 plus TK. Its manual tells providers to show the number of riders through the units on the line.

TK, TT, and GM are not interchangeable

The national labels only set the frame. South Dakota lists GM for ambulances with no payment effect, yet its fee schedule prices additional ambulance recipients with TK. The payer’s own modifier list and fee schedule are what count.

Before adding TK to a line

1. Check that the state fee list, or the broker’s rate sheet, shows your base code with TK beside it. If that pairing is missing, leave TK off.
2. Pin down who TK stands for in that program: a second member, a companion, an attendant, or a rider count.
3. Check whether the extra person earns any mileage. In South Dakota, and for a second member in Indiana, the answer is no.
4. Write the extra person into the trip record, with name, relationship, and any approval number.

For escorts and attendants generally, and for sharing a vehicle among riders, see multi-loading.

Knowing who rides along

A TK line holds up best when the extra person was on the trip record before pickup. HealthRide tracks seats, wheelchair spaces, and escorts on each trip, so the dispatch board shows who is riding along before the vehicle leaves.