USPS + ReturnMate
USPS is the cost-effective default for US domestic returns, particularly for lightweight parcels under one pound where private couriers price uncompetitively. ReturnMate connects to USPS's modern REST API for label generation, live rate quoting, address validation, and free package pickup scheduling. Currently in Beta — production-ready for domestic US, with international service expansion landing in upcoming releases.
What the USPS connection actually does.
- USPS REST API integration with API key authentication
- Domestic US labels — Priority Mail, Ground Advantage, Priority Mail Express
- International labels — First-Class Package International, Priority Mail International
- Free Package Pickup scheduling — no fee for inbound returns at the customer's door
- Live rate quoting at the customer portal
- Address validation with ZIP+4 standardisation
- Limitation: very restrictive on dangerous goods — lithium batteries face tight ground-only rules; route DG via FedEx or UPS
Where it earns its place.
Cost-effective US domestic returns
For non-DG returns under 1lb, USPS Ground Advantage is meaningfully cheaper than FedEx or UPS Ground. ReturnMate rate-shops at the customer portal and surfaces USPS as the default for qualifying parcels.
Free pickup at the customer's door
USPS Carrier Pickup is free for inbound returns when bundled with regular mail delivery. ReturnMate books the pickup automatically when the customer chooses USPS at the portal — no separate pickup fee, no separate booking flow.
Lightweight US-origin international
For US merchants with international customers, USPS First-Class Package International is the cost-effective option for sub-4lb parcels. Useful for returns from Canada, Mexico or APAC customers.
PO Box delivery support
USPS is one of the few US carriers that delivers to PO Boxes and APO/FPO military addresses. ReturnMate detects these address types and routes automatically when private couriers wouldn't accept them.
How USPS gets connected.
Carrier accounts are set up by our team, not by you. We contact USPS directly, obtain API access against your existing commercial account, and apply it — so you never have to source or handle API credentials.
- You send us three things
Your existing USPS account number, written authority for ReturnMate to contact them on your behalf, and your account manager's name, email and phone number.
- We contact USPS
Our support team requests API access against your account and handles the paperwork and technical back-and-forth with the carrier.
- We apply the credentials
Credentials are stored encrypted against your shop. They are never shown to you and never need to be — there is nothing for you to paste or maintain.
- We test it end to end
We generate a test label — including the dangerous goods transport document where it applies — and confirm it works before the carrier goes live for your team.
Turnaround varies by carrier, depending on how quickly they issue API access. Support confirms the expected timeline for USPS when you start onboarding. Don't have an account with them yet? We can help you set one up.
Questions about USPS.
When should I use USPS over FedEx or UPS?
For US domestic non-DG parcels under one pound, USPS Ground Advantage is consistently the cheapest option. Above one pound the comparison gets closer and depends on your negotiated rates with the private couriers. ReturnMate rate-shops automatically — for any specific shipment, the cheapest accepting carrier is offered to the customer.
Does USPS handle lithium battery returns?
Very restrictively. USPS has tight rules on lithium batteries — installed batteries (in a device) up to specific watt-hour ratings can ship ground-only with proper labelling, but standalone batteries or air shipments are largely prohibited. For lithium-powered product returns, ReturnMate routes via FedEx or UPS, both of which have broader DG capability. USPS is blocked for those SKUs.
Is USPS Free Package Pickup actually free?
Yes, when the carrier is already delivering mail to the address. There's a separate USPS Pickup On Demand service for guaranteed pickup at a chosen time which carries a fee. ReturnMate uses the free Carrier Pickup by default and surfaces the paid On Demand option for time-sensitive cases.
When is USPS coming out of Beta?
Beta status reflects ongoing feature expansion (international service refinements, advanced rate optimisation, USPS Pickup On Demand integration), not stability concerns. The integration is production-deployed today for US domestic returns. Exit-Beta target depends on feedback from merchants currently using it; we'll move the badge once feature surface reaches parity with the AU carriers.
Ask about the USPS integration.
Tell us how you ship with USPS
Volumes, lanes, whether you already have an account — we'll come back within one business day.
Often set up together.
FedEx
Global Ship/Rate/Track/Pickup for US, Canada, EU and rest-of-world. OAuth2 REST API for non-AU merchants.
View integration →CarriersUPS
Global Ship/Rate/Track/Pickup for US, Canada, EU. OAuth2 Basic Auth REST API as a primary or backup non-AU carrier.
View integration →CarriersCanada Post
Canadian national post — domestic and international labels, address validation, tracked rates. REST API for Canadian merchants.
View integration →CommerceShopify
Native install with orders, customers, inventory, refunds, draft orders, and mandatory-webhook compliance.
View integration →Wire your stack together.
Start free — 5 returns a month on the Free plan, no credit card required. Billed through Shopify.