323 Mailer Responsibility

323.1 General

Full responsibility rests with the mailer to comply with all Postal Service and non-Postal Service laws and regulations in mailing hazardous material. Anyone who mails, or causes to be mailed, a nonmailable or improperly packaged hazardous material may be subject to legal penalties (i.e., fines and/or imprisonment), including but not limited to those specified in 18 U.S.C. Transporting hazardous materials before entry as U.S. Mail and after receipt from the Postal Service is subject to DOT regulations.

323.2 Service Type Codes

Mailers tendering to the Postal Service packages containing hazardous materials must use a unique Service Type Code (STC) for domestic outbound and return packages that corresponds to the product being shipped (e.g., Priority Mail, Parcel Select Lightweight, and USPS Ground Advantage). The STC is required regardless of whether mailpieces are entered at origin or for destination entry. If purchasing an eligible extra service, mailers must use the STC indicating the product and extra service. Extra services permitted with hazardous materials mailings are:

  1. Signature Confirmation.
  2. Insurance less than or equal to $500.
  3. Insurance over $500.
  4. Signature Requested for Priority Mail Express.
  5. Adult Signature over 21 for Priority Mail Express (tobacco/Electronic Nicotine Delivery System [ENDS] products).
  6. Adult Signature over 21 for Priority Mail (ENDS products).

A list of HAZMAT STCs and ESCs is in Appendix G and Pub 199.

323.3 Extra Service Codes

Mailers tendering to the Postal Service packages containing hazardous materials must use ESC 857. Mailers may optionally use one of 23 unique content-specific Extra Service Codes (ESC) for domestic outbound and return packages that corresponds to the specific category of hazardous material contained within the mailpiece. If one of the content-specific ESC is used, then ESC 857 may be omitted when not enough extra-service code fields are available for the package details. A list of ESCs is in Appendix G and Publication 199.

Note: While using the content-specific ESC is currently a recommended practice, the Postal Service may make this requirement mandatory in the future.

323.4 Additional GS1 DotMatrix (2D) IMpb

Effective January 21, 2024, in addition to including the appropriate STC in the one-dimensional GS1-128 IMpb barcode on the address label, the Postal Service requires adding two (2) supplemental GS1-DataMatrix (2D) IMpbs to domestic shipping labels for mailpieces containing hazardous materials — one in the address block to the left of the delivery address and one in the lower right corner of the shipping label. For more information on the GS1-DataMatrix (2D) IMpbs, see GS1 (2D) information and barcode specifications at https://www.gs1.org/docs/barcodes/GS1_DataMatrix_Guideline.pdf and https://postalpro.usps.com/shipping/impb/2d-impb-guide.

323.5 Shipping Service File

Mailers shipping hazardous materials domestically utilizing PC Postage, eVS, USPS Ship, and/or ePostage platforms must incorporate the applicable Service Type Code (STC) and/or Extra Service Code (ESC) listed in Appendix G and Publication 199 and transmit a Shipping Services File (SSF), using Version 1.7 or higher, or Shipping Partner Event File (SPEF), using Version 5.0 or higher, to the Postal Service before, or concurrent with tendering any hazardous materials shipments.

323.6 Legacy Postage and Hard-Copy Postage Statements

Mailers using legacy postage meters or hard-copy postage forms must present hazardous materials mailings to a Postal Service retail or business mail entry unit for acceptance.

323.7 USPS-Generated Shipping Labels

At the time of label generation, mailers using a label that USPS generated (including but not limited to USPS APIs, WebTools, Click-n-Ship, or Merchant Returns Application) must indicate whether the shipment contains hazardous materials.