All tires manufactured for use in the United States are required to display certain standardized information along the sidewall. One piece of this information is the U.S. Department of Transportation (DOT) Tire Identification Number.
DOT numbers begin with the letters "DOT" followed by a series of 10 to 12 letters or numbers. By law, they are branded into the sidewall of every tire sold in the United States.
The series of numbers or letters that make up the DOT number tell consumers the manufacturing location, tire size and when the tire was manufactured.
The first two numbers or letters after "DOT" are a code for the plant at which the tire was manufactured.
The last four numbers tell you when the tire was made based on a certain week in a given year. For example, "2306" means the tire was made during the 23rd week of 2006.
The numbers or letters in between are used by the manufacturer for marketing or identification purposes. This portion is used in the event of a recall to contact consumers.
While some may call the DOT number a tire's serial number, the two are not technically the same. Serial numbers identify one item, while DOT numbers identify entire batches of tires that were produced at the same time.
By federal law, every tire sold in the U.S. must have a DOT number. They are usually only on one sidewall of a tire, so if you do not see your tire's DOT number, it could be because it is on the sidewall facing the inside of your vehicle.
