Does every tire come with a DOT number?

Every tire has a Department of Transportation number, beginning with DOT, on one sidewall. As of April 2015, the first two digits or letters reveal the tire manufacturer. For tires manufactured after January 1, 2000, the last four digits of the number identify the week and year it was manufactured.

A tire manufactured in the 14th week of the year 2010 has the last four numbers 1410. Before January 1, 2000, the last three digits of the DOT number identified the week and the year the tire was manufactured. A tire manufactured in the 26th week of 1999 has the last three numbers 269.