Make sure there really isn't a spare
Look under the cargo floor panel first, then behind the side trim in the trunk. On many trucks and SUVs the spare hangs under the rear of the vehicle and is lowered with a crank. The owner's manual shows where it is and how to lower it.
If it isn't anywhere, you probably have a car that skipped the spare to save weight and room. Carmakers usually replace it with an inflator and sealant kit, or with run-flat tires.
While you're looking, read the size off the tire's sidewall. It's a string like P225/65R17, and it's the one detail a supplier needs to find a match. A photo of it on your phone saves a trip back out to the car later.
If your car has a sealant and inflator kit
The kit is meant for a small puncture in the tread. You attach it, run the compressor and the sealant coats the hole from the inside. It's a short-term fix, with speed and distance limits printed on the kit, and the sealant has an expiration date that people forget to check.
It can't help with a sidewall cut, a torn tire or a large hole. If you use it, tell whoever repairs the tire afterward, because the sealant coats the inside and can complicate the repair.
If your car has run-flat tires
Run-flat tires have reinforced sidewalls that hold the car up for a limited distance after the air is gone, commonly around 50 miles at no more than 50 mph. The manual gives your car's numbers. The tire warning light is how you find out.
A run-flat that has been driven low or flat often has to be replaced instead of repaired. Check with the tire maker or a shop before assuming it can be saved.
Having a tire brought to you
With no spare and a tire that can't be sealed, the choices are a replacement tire delivered to you or a tow to a shop. TRA's tire replacement supplies the tire and installs it where you're parked, so you don't need a usable spare in the vehicle. It's from $129, plus a $19 dispatch fee charged once per job.
Tire availability varies, and dispatch confirms a tire is available, and your total, before a driver is sent. Have the tire size ready. It's printed on the sidewall, and the driver's door jamb sticker lists it too. We don't tow, so if the wheel itself is damaged or the car can't be driven for another reason, you'll need a tow company.
Don't drive to a shop on a flat to avoid the wait. A car sitting where it is can wait for a tire to come to it, and a tire driven flat is often ruined, and sometimes the wheel too.
Common questions
A flat tire change puts on the spare you already carry, so it needs one. Without a usable spare, ask for tire replacement instead, where we supply a tire and install it.
The year, make and model, your exact location, the tire size if you can read it, and whether the car has run-flat tires. Those details help dispatch confirm that a tire is available.
For a short distance at the kit's speed limit, to get to a repair. It isn't a permanent fix, and the tire should be looked at soon.