Setting Up USPS Shipping Rates

USPS Shipping Rates

BuySellBid can show your buyers real-time USPS rates at checkout — Ground Advantage, Priority Mail and Priority Mail Express — calculated live from your origin to the buyer's ZIP. To enable this, you need to get USPS API credentials from the USPS Developer Portal and paste them into your seller dashboard.

The whole setup takes about 15 minutes. There are three steps.

Step 1 — Register for a Business Customer Gateway (BCG) account

The Business Customer Gateway is the single sign-on hub for all USPS business services. This is not the same as a regular USPS.com account — even if you already have a USPS.com login for buying stamps, you need a separate BCG account to access the API.

1. Go to gateway.usps.com
2. Click Sign up for the BCG
3. Enter and verify a business email address
4. Create a USPS.com Business Account (follow the on-screen prompts)
5. Enter your company information, contact information and security settings
6. Accept the Terms and Conditions
7. Complete the sign-up

Approval is generally instant. At the end you will be assigned a CRID (Customer Registration ID) and possibly a MID (Mailer ID). Save these somewhere safe — you do not need them for rate calculations, but you will need them later if you ever add USPS label printing or tracking.

Step 2 — Create an App in the Customer Onboarding Portal

The actual API credentials live in a separate USPS site called the Customer Onboarding Portal (COP).

1. Go to cop.usps.com
2. Sign in using the BCG credentials you just created
3. On the landing page, find the Getting Started section and click Developer Apps
4. Click Add App
5. Fill in the form:
   • App name — anything you like, for example BuySellBid Shipping
   • Callback URL — leave blank
   • Accept the Terms and Conditions
   • Description is optional
   • Leave the default API product selected — it includes Domestic Pricing, which is what BuySellBid needs
6. Click Add App to finalise
7. Back on the apps list, click Manage next to your new app (not the app name — the Manage button)
8. Find the Credentials section. You will see two values:
   • Consumer Key — a long string, this is your client ID
   • Consumer Secret — another long string, this is your client password
9. Copy both values

Important: The Consumer Secret is only shown in full at the moment of creation. If you lose it, you will need to reset it on the app to get a new one. Save it somewhere safe immediately.

Step 3 — Add the credentials to BuySellBid

1. Sign in to BuySellBid
2. Go to Dashboard → Shipping Setup
3. In the carrier section, find the USPS card
4. Paste your Consumer Key into the USPS Consumer Key field
5. Paste your Consumer Secret into the USPS Consumer Secret field
6. Click Save

That is it. Your buyers will now see live USPS rates at checkout, calculated automatically from your ship-from ZIP to their delivery address.

What buyers see

At checkout, buyers entering a US ZIP will see three USPS options sorted cheapest first:

• USPS Ground Advantage — the cheapest option, 2–5 business days
• USPS Priority Mail — 1–3 business days, includes $100 of insurance
• USPS Priority Mail Express — fastest, 1–2 business days

The price they see is the live USPS retail rate plus your handling fee if you have one set.

Rate limits to know about

The default USPS API tier allows 60 calls per hour. Each rate quote on BuySellBid uses 3 calls (one per service class), so you can serve roughly 20 rate quotes per hour before USPS starts returning errors. Each seller has their own quota — your limit is not affected by other BuySellBid sellers.

If you hit the limit regularly, request a quota increase directly from USPS API Support — it is free but reviewed manually so it can take a few days.

International orders

USPS rates on BuySellBid currently support US destinations only. International USPS shipping uses a different USPS endpoint and is not enabled yet. If a buyer outside the US is checking out, they will see your flat rate, free shipping or UPS rates if you have UPS configured.

Troubleshooting

• "USPS authentication failed" — the Consumer Key or Secret is wrong, or the Secret was only shown once and you saved a partial value. Go back to cop.usps.com → Manage your app → reset the Secret, then paste the new one.
• No rates appear at checkout — make sure your Ship From ZIP is set in Dashboard → Shipping Setup. USPS cannot calculate rates without an origin ZIP.
• Some weights or sizes return no rates — USPS has size and weight limits per service class. A 70+ lb package or a very oversized parcel may not be eligible for some services.
• Rates suddenly stop working — most likely you hit the 60 calls per hour limit. Wait an hour and they will return.

Why USPS instead of UPS?

You can offer either or both. USPS is generally cheaper for small, light packages under one pound. UPS is generally better value for heavier packages. Many BuySellBid sellers offer both and let the buyer choose.

What about printing labels?

Label printing through USPS requires additional setup including a USPS Ship enrolment and an Enterprise Payment Account. This is not enabled in BuySellBid yet — for now, generate your USPS labels at usps.com/ship or your preferred shipping platform, then enter the tracking number on the order in your dashboard.