Toto manufactures many plumbing products, including many innovative lines of toilets. If you want to replace your current Toto toilet with a similar but newer style or you need to find a replacement part for your toilet, you need to know its specific model; not all the parts used on one Toto toilet are interchangeable with other Toto toilets. The model of the toilet is printed on the fixture itself--refer to this data before ordering replacement parts.
Lift the lid off the Toto's water tank. Turn the lid over.
Look on the underside of the lid for a black ink stamp. You will see "ST" or "CST," followed by three numbers. This is the model of your toilet. Proceed to Step 3 if you don't find the stamp on the lid.
Look inside the toilet tank. The model identification stamp is placed on one of the inside walls if it is not on the underside of the lid.
Contact Toto (totousa.com) if you do not see a stamp. This may have happened due to human error during manufacturing.