TT Modifier: Billing More Than One Rider on the Same NEMT Trip

What the TT modifier means

CMS lists TT in the national HCPCS code set as “Individualized service provided to more than one patient in same setting.” It was added on October 1, 2002, and the October 2026 quarterly file gives it coverage code I, which means Medicare does not pay it.

The national description names no vehicle, no base code, and no rate. Each Medicaid program, and each broker or plan paying under it, decides whether TT belongs on a ride claim. Indiana’s fee-for-service program is one that uses it, for the second and later members on a shared trip.

Several codes sit close to TT, and a payer that wants one may deny another:

• TT: another member who shares the ride, billed on that member’s own claim.
• TK: “Extra patient or passenger, non-ambulance.” Indiana uses it for a parent or attendant riding with the member. See the TK modifier.
• UN, UP, UQ, UR, US: two, three, four, five, or six or more patients served. Medi-Cal uses these on shared wheelchair van rides. See U modifiers.
• GM: “Multiple patients on one ambulance trip,” for ambulances only.
• T2004: a base code, not a modifier: “Non-emergency transport; commercial carrier, multi-pass.” Indiana bills it for later riders on a walk-on trip. See T2004.

How Indiana pays TT on a shared ride

Indiana’s Transportation Services module (version 6.1, published August 19, 2025) sets the rule. When you carry two or more members at the same time, from the same county to the same vicinity, such as different buildings on one medical campus, the first member pays in full: base rate, loaded miles, and waiting time. Each later member pays half the base rate, with no mileage and no waiting time.

Two limits apply. Indiana pays nothing for multiple passengers in ambulances or family-member vehicles. And it pays nothing extra for a shared ride if you do not bill your other customers for multiple passengers.

Each later rider’s code is the first rider’s code with TT added, except on walk-on trips, which switch to T2004. These are Indiana’s fee-for-service rates for the later rider:

Type of ride	First member	Each later member	Later member pays, 2026 / 2027
Wheelchair van	A0130, plus A0425 U5 mileage	A0130 TT	$15.90 / $16.36
Taxi, 0 to 5 miles	A0100 UA	A0100 UA TT	$3.81 / $3.92
Taxi, 6 to 10 miles	A0100 UB	A0100 UB TT	$6.36 / $6.54
Taxi, 11 miles or more	A0100 UC	A0100 UC TT	$9.54 / $9.82
Walk-on (commercial ambulatory)	T2003, plus A0425 U3 mileage	T2004, no TT	$6.36 / $6.54

The 2026 rates took effect January 1, 2026 on the professional fee schedule updated September 8, 2026. The 2027 rates are on the NEMT fee schedule effective January 1, 2027. For comparison, a solo wheelchair van base, A0130, pays $31.79 in 2026 and $32.71 in 2027.

The taxi lines are for taxis whose fares no local ordinance sets. Indiana pays those taxis the lower of the charge or the amount shown. A taxi with a city-set metered or zoned fare bills that fare, paid up to the maximum.

Prior authorization for a base code also covers its matching shared-ride code. If a trip turns into a shared ride at the last minute, you need only the right code, not a new approval.

Most fee-for-service NEMT in Indiana is brokered by Verida, and you bill those trips to Verida, not the state. The module says Verida’s rate schedule is based on the IHCP Professional Fee Schedule, each provider signs a Verida rate agreement that lists its rates, and Verida may negotiate higher or special rates. Check your agreement for the shared-ride lines before you count on the amounts above.

A worked example: two riders in one taxi

Two members live in the same apartment building and go to the same dialysis center, 8 miles away, for the same chair time. One taxi carries both. Each member gets a separate claim, and both trips fall in the 6 to 10 mile band, UB. Indiana also wants an origin and destination modifier on every base code, here RJ for residence to a freestanding dialysis facility. For a taxi whose fares no local ordinance sets, the two claims pay up to:

Claim	Codes	Pays in 2026	Pays in 2027
First member	A0100 with UB and RJ	$12.71	$13.08
Second member	A0100 with UB, TT, and RJ	$6.36	$6.54
Total		$19.07	$19.62

Two separate taxi trips would pay $25.42 in 2026. The shared trip pays $6.35 less, and the car makes one run instead of two. Neither claim bills mileage, because Indiana does not pay taxi mileage, though the driver still records the distance.

Indiana’s driver ticket rules apply to each rider: the member’s name, pickup address, Medicaid ID, and signature, the drop-off provider’s name and address, the driver’s name, and odometer readings or mapped miles. Indiana wants that record behind every claim, so a shared ride needs it for each member on board.

If the same member rides alone one way and shares the ride the other way, the shared trip is a separate encounter. The module gives the walk-on case: bill the solo trip on T2003 and the shared trip on T2004 with the XE modifier. The module says modifier 59 is not appropriate there. See the XE modifier for second trips on the same day.

How other programs bill a second rider without TT

Many programs mark a shared ride another way:

• Medi-Cal fee-for-service. A0130 takes UN for two patients, UP for three, and UQ, UR, or US for four, five, or six or more, on each rider’s claim. The maximum per patient is $16.22, $12.85, and $11.51, against $20.30 for one rider (rate page updated September 2023). Mileage (A0380) goes only on the first rider’s claim. Each claim carries an attachment with the other riders’ names and Medi-Cal ID numbers, which may not go in box 19, and each rider needs a treatment authorization request that lists every rider on the trip. The rule covers only riders picked up at a common point and taken to the same destination.
• South Dakota. A second Medicaid rider bills the base code with TK, paid at 50 percent of the fee on the modifier list effective July 1, 2026. Only one mileage allowance is billable per trip, on one rider’s claim. See the TK modifier for the math.
• Brokers and health plans. Shared rides follow the broker’s rate sheet and codes. See NEMT multiloading for planning shared runs and how each payer prices them.

How to bill TT without a denial

1. Find the TT line. Look for your base code with TT on your fee schedule or broker rate sheet. A pair your payer does not list can deny with reason code 4, “The procedure code is inconsistent with the modifier used.”
2. Check that the trip qualifies. In Indiana the riders travel at the same time, from the same county to the same vicinity, in one wheelchair van, walk-on vehicle, or taxi.
3. Bill the first rider in full. The base rate, the mileage, and any waiting time go on the first member’s claim.
4. Bill each later rider on a separate claim. Use the base code with TT and no mileage or waiting time, or T2004 on a walk-on trip.
5. Keep the origin and destination modifier. Each base code still needs one. A0100 with UB, TT, and RJ fills three of the four modifier spaces in box 24D of the CMS-1500. See NEMT billing codes for the base codes.
6. Use the rate for the date of service. Indiana’s A0130 TT rises from $15.90 to $16.36 on January 1, 2027.