The “M” numbers issued by U.S. DOT to hazmat packaging providers are registered symbols that substitute for the company’s name and address when marking hazmat packagings with required information. Recently, DOT stopped issuing “R” numbers, although existing “R” numbers remain valid (unless they were individually canceled).
For a connection to DOT’s online Search tool for “M” numbers showing company names, addresses and renewal dates, click here.
For a list of “R” numbers and their registered holders, simply click here.
For information on how to apply for an M number, click here.