The Federal Motor Carrier Safety Administration (FMCSA) is issuing this advisory to motor carriers and shippers of hazardous materials requiring a Hazardous Materials Safety Permit (HMSP) pursuant to 49 CFR § 385.403. This advisory is intended to clarify when FMCSA will issue a HMSP and the process when a motor carrier has been issued a HMSP and no longer transports materials requiring a HMSP. This advisory also serves as a reminder to motor carriers as to the proper procedures for applying for and renewing a HMSP.  Finally, this advisory addresses whether a HMSP is required for the transportation of anhydrous ammonia.