USPS Ship Guide

USPS Ship is a USPS integration that enables live rates and label generation through EasyPost using USPS-provided credentials. Rates and labels are generated by USPS systems and returned through the EasyPost API.

Sign up for an EasyPost account to obtain a Test and Production API key. See Authentication and Key Management for more information.

USPS Ship carrier accounts are added using an OAuth flow. During setup, users are redirected to USPS to authorize EasyPost. After authorization, USPS provides account identifiers, such as EPA, CRID, and MID, which are used to complete account configuration.

• Enterprise Payment Account (EPA): A USPS-managed account configured with negotiated rates, allowing EasyPost to generate designated pricing. Although technically a payment account, USPS is only using this to manage rate cards, so there is no need to fund the EPA. EasyPost manages all payments via EasyPost Wallet.
• Customer Registration ID (CRID): A unique identifier automatically assigned by USPS when a business creates a USPS account.
• Mailer ID (MID): A 6-digit or 9-digit identifier assigned by USPS to a shipper. Used to identify the mailer on outbound shipments and in manifest submissions. High-volume shippers whose volume is 200,000 pieces or more annually must obtain a 6-digit MID directly from USPS, which provides a larger pool of unique tracking codes and helps avoid duplication at scale.
• Manifest Mailer ID (Manifest MID): A MID designated for manifest submissions. Depending on account configuration, this may be the same as the primary MID or a separate value.
• Returns Mailer ID (Returns MID): A MID designated for return label generation. Required when the account is enrolled in USPS returns services and used to identify the return destination on USPS return labels.

USPS Ship supports different account configurations, including:

• Direct Negotiated Service Agreement (NSA): A Direct NSA is a negotiated contract between USPS and a high-volume shipper (e.g., large retailer or enterprise). The shipper has a direct relationship with USPS and uses their own negotiated rates.
• Connect eCommerce (CeC) NSA: A CeC NSA is a negotiated USPS contract with a platform or marketplace. The platform gets discounted USPS rates, sells postage to merchants at a higher merchant rate, and earns commission from the difference.

Refer to the following guides for setup instructions:

• USPS Ship Carrier Account (NSA)
• USPS Ship Wallet Carrier Account (CeC Platform)

Download an EasyPost Client Library or utilize the REST API with cURL.

Examine the EasyPost Objects section to understand the API's structure, which is critical for constructing requests and interpreting responses.

USPS Ship is a Live Rating integration, enabling real-time rate retrieval for shipments created via EasyPost.

• When creating a shipment, EasyPost requests USPS for shipment rates specific to the user’s USPS account or contract.
• The rates provided are directly from USPS and tailored to the user's specific account details.

EasyPost does not participate in the billing process for USPS Ship. Users should contact a USPS representative with any inquiries.

USPS Ship is billed through EasyPost Wallet.

• Postage payment, adjustments, and refunds are processed by EasyPost Wallet.
• Rate cards and contract configuration are managed directly by USPS.

USPS Ship offers the following service levels:

• GroundAdvantage
• Express
• Priority
• First
• LibraryMail
• MediaMail

• FirstClassPackageInternationalService
• PriorityMailInternational
• ExpressMailInternational

USPS Ship has several predefined packages supported by EasyPost.

• FullPostalPaks
• HalfPostalPaks
• HalfTrayBox
• PMODSack
• Pallet
• FullTrayBox
• EMMTrayBox
• FlatTubTrayBox

• FlatRateEnvelope
• FlatRateLegalEnvelope
• FlatRatePaddedEnvelope
• FlatRateWindowEnvelope
• FlatRateCardboardEnvelope
• SmallFlatRateEnvelope
• Parcel
• SoftPack
• SmallFlatRateBox
• MediumFlatRateBox
• LargeFlatRateBox
• LargeFlatRateBoxAPOFPO

• FlatRateEnvelope
• FlatRateLegalEnvelope
• FlatRatePaddedEnvelope
• FlatRateWindowEnvelope
• FlatRateCardboardEnvelope
• SmallFlatRateEnvelope
• Parcel
• SmallFlatRateBox
• MediumFlatRateBox
• LargeFlatRateBox

• Maximum weight limit: 70 pounds.
• Maximum dimensions: 108 inches combined length and girth.
• Exception: USPS Ground Advantage™ mailpieces may measure up to 130 inches in combined length and girth.

• Maximum weight and size vary by destination country.
• Dimensions and weight limits can be determined using the USPS Postage Calculator(opens in a new tab).

With EasyPost, generating shipping labels for USPS Ship is the same process as generating them for any other carrier.

Review the Getting Started Guide for help generating a shipping label.

One-call buys enable streamlined label purchasing through the EasyPost API by consolidating multiple operations into a single API request. This feature is designed to simplify and accelerate the shipping process by combining the creation of a shipment, retrieval of rates, and purchasing the shipping label into one efficient step.

See Reducing API Response Times for more information.

• address_validation_level
• additional_handling
• entry
• special_rates_eligibility
• live_animal
• endorsement
• machinable
• certified_mail
• return_receipt
• label_date
• delivery_confirmation
• label_size
• hazmat
• carrier_insurance_amount
• print_custom_1, print_custom_2, print_custom_3

USPS recommends creating a ScanForm to consolidate shipments for acceptance. However, manifesting is not required for USPS Ship, and labels are valid upon creation.

ScanForms can be created using the ScanForm endpoint or as part of a Batch.

Voiding USPS Ship labels through EasyPost is supported.

EasyPost offers USPS Ship labels in PDF, PNG, and ZPL formats.

• Domestic: 4 x 6 and 4 x 5
• International: 4 x 6

This guide does not specify handling hazardous materials with USPS Ship. Please review the USPS Carrier Guide for specific USPS guidelines, shipping restrictions, and requirements.

• AIR_ELIGIBLE_ETHANOL
• CLASS_1
• CLASS_3
• CLASS_7
• CLASS_8_CORROSIVE
• CLASS_8_WET_BATTERY
• CLASS_9_NEW_LITHIUM_INDIVIDUAL
• CLASS_9_USED_LITHIUM
• CLASS_9_NEW_LITHIUM_DEVICE
• CLASS_9_DRY_ICE
• CLASS_9_UNMARKED_LITHIUM
• CLASS_9_MAGNETIZED
• DIVISION_4_1
• DIVISION_5_1
• DIVISION_5_2
• DIVISION_6_1
• DIVISION_6_2
• EXCEPTED_QUANTITY_PROVISION
• GROUND_ONLY
• ID8000
• LIGHTERS
• LIMITED_QUANTITY
• SMALL_QUANTITY_PROVISION

• CLASS_7
• CLASS_9_UNMARKED_LITHIUM
• DIVISION_6_2

Pickups are not currently supported for USPS Ship through EasyPost.

EasyPost simplifies package tracking by offering two methods:

• Tracking with an existing number and carrier.
• Using a Tracker included with an EasyPost-purchased shipping label.

The service integrates webhooks for timely shipment updates. For detailed information on tracking methods, visit the Tracking Guide.

The Carrier Metadata endpoint can programmatically return information about service levels, predefined packages, supported features, and shipment options.

Use this information to quickly integrate and make educated decisions about the mix of carriers for shipping needs. Additionally, the Carrier Metadata endpoint is available to retrieve comprehensive information about all carriers on the EasyPost platform, enhancing decision-making for carrier services.

In addition to the guidance provided in our Carrier Guides, EasyPost offers support to assist with FAQs, troubleshooting issues, and inquiries related to the EasyPost platform.

Please visit the Help Center for more information.

For questions about getting started with the EasyPost API please talk to a Shipping Expert or contact our Support team.