Live checkout rates for Shopify

Updated 2026-10-22

Send live NitroMule carrier rates to Shopify checkout. Shopify calls this a CarrierService (app-calculated rates). It only works when Shopify has third-party carrier-calculated shipping (CCS) enabled for the store.

Requirements

• Connected Shopify store in NitroMule
• Default ship-from address in NitroMule
• Product weights set in Shopify
• Package dimensions available to NitroMule (see below)
• Shopify plan that allows CCS:
  • Advanced or Plus — included
  • Grow — yearly billing includes CCS, or ask Shopify Support to add CCS for a monthly fee
  • Basic / Starter — not available

NitroMule cannot turn CCS on for you. That switch lives only on Shopify’s side.

Enable CCS in Shopify (if Save fails)

If NitroMule shows an error like “Carrier Calculated Shipping must be enabled for your store before enabling: NitroMule Rates”:

1. Confirm your plan qualifies (see above).
2. Contact Shopify Support and ask them to enable third-party carrier-calculated shipping for your store.
3. Return to NitroMule → Stores → Shopify → turn on Send NitroMule rates to Shopify Checkout → Save.

Product dimensions

Shopify’s product Packaging dropdown (“Store default · Sample box…”) is not readable via the Admin API, so NitroMule cannot copy that box. Per-variant L/W/H of 0 also means “unset.”

On connect, NitroMule creates (and pins) empty Package length / width / height metafield definitions on variants (custom.length, custom.width, custom.height) — same keys ShipStation uses. Open a product → open the variant → Metafields → enter the box size. Values stay empty until you fill them — we don’t invent sizes or copy Shopify’s Packaging dropdown.

Also accepted if you already use them: shipping.* or nitromule.* with the same keys. Or assign a Package on the NitroMule product.

Weight comes from the Shopify product weight on the order line.

Existing installs: after we add this, reconnect Shopify once (new write_products scope) so definitions can be created.

Turn on rates in NitroMule

1. Open Stores → Shopify (connected store).
2. Enable Send NitroMule rates to Shopify Checkout → Save.
3. NitroMule registers the NitroMule Rates carrier service with Shopify.

Add NitroMule Rates to shipping zones

After Save succeeds:

1. In Shopify Admin, go to Settings → Shipping and delivery.
2. Open the shipping profile / zone that covers the countries you sell to.
3. Add a rate that uses carrier or app rates and select NitroMule Rates (wording varies slightly by Shopify admin version).
4. Save.

Until the method is on a zone, shoppers will not see NitroMule rates at checkout even if the NitroMule toggle is on.

Test at checkout

1. Add a physical product to the cart on your storefront.
2. Enter a shipping address in a covered zone.
3. Confirm NitroMule carrier services appear with prices.
4. Place a test order, then Sync in NitroMule and confirm the requested service imported.

Checklist

• Default ship-from set in NitroMule
• Shopify store connected
• CCS available on the Shopify plan (or enabled by Shopify Support)
• Send NitroMule rates saved successfully in NitroMule
• NitroMule Rates added under Shipping and delivery
• Test checkout shows live services

Troubleshooting

Shopify’s own overview: Setting up shipping zones and rates.