USPS Shipping Rates Not Showing or Intermittent at Checkout
If USPS shipping rates are not appearing at checkout, appear inconsistent, or occasionally fail to load, this is typically related to how the United States Postal Service (USPS) API handles request limits.
Why This Happens
USPS provides real-time shipping rates through their API. While limits are not always formally published, USPS may restrict or throttle requests when too many are sent within a given period.
In Spirit Sale, this can occur more easily because:
- Each checkout session can generate multiple rate requests
- Refreshing checkout or updating an address triggers additional requests
- Spirit Sale uses the same USPS API credentials across multiple stores
- Activity across those stores contributes to a shared request limit
Based on industry experience and USPS API behavior, most accounts operate around a default limit of approximately 60 requests per hour, unless a higher limit has been approved.
When request volume exceeds this level, USPS may:
- Return no available shipping methods
- Return incomplete or delayed results
- Temporarily reject requests
Important to Know
- This behavior originates from USPS and is outside of Spirit Sale’s control
- All stores using the same USPS credentials contribute to a shared usage limit
- This means limits can be reached even if a single store has moderate traffic
- The issue is often temporary and resolves automatically
Common Scenarios
- Customers reload refresh the checkout page multiple times
- Customers enter or modify their address repeatedly
- Your store(s) have multiple customers checking out at the same time within a short span of another (Generally within an hour)
What You Can Do
- Retry after a short wait - In many cases, waiting briefly and refreshing checkout will allow USPS rates to return.
- Provide backup shipping options - To prevent checkout disruption, consider enabling Flat rate shipping or free shipping options.
- Request a higher USPS API rate limit - If this issue occurs frequently, your USPS account may be reaching its default usage limits. You can contact USPS API support to request an increase by emailing apisupport@usps.gov.
Please note: Approval of increased limits is determined by USPS and is not guaranteed.
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