Recalculate shipping fees based on choose delivery date

Retired Boards Appdev Extensions

Topic summary

Main issue: recalculating shipping fees when a customer selects or changes a delivery date during checkout.

Context: a custom CarrierService returns delivery options and prices based on items, postcode, and delivery date. Previously, the store set shippingAddress and checkoutLineItems.attributes (delivery date) via the Storefront API before checkout so rates were correct.

Desired flow with checkout extensibility: customer enters address, selects a delivery date via a date picker; the date is saved to cart line item attributes; shipping options and fees are recalculated and shown for that day.

Progress: the date picker is implemented using Checkout UI Extension (Shopify’s new checkout extensibility) and the selected date is successfully added to cartLineItems.

Key request: how to programmatically trigger shipping price recalculation after the delivery date is selected/changed, similar to recalculation on address changes.

Status: no resolution or action identified yet; the question remains open. An attached image illustrates the date picker UI but is not critical to the technical issue.

Summarized with AI on December 30. AI used: gpt-5.
1

Our store offers different delivery options as well as different prices based on the items, postcode and delivery date. We have our own CarrierService that uses this data to return the available options and prices.

We currently add the delivery address to the checkout(shippingAddress) and the delivery date chosen by the customer to the attributes of the order items(checkoutLineItems.attributes), using storefrontAPI before getting to the checkout, this way the price is calculated correctly using this information.

Our goal is to remove this previous step and using the new checkout extensibility features, add a dataPicker to the checkout.

The flow would be something like this:

  1. Customer arrives at checkout
  2. Customer fills in the address
  3. Select the delivery date
    1. We update the cartLineItems by adding the chosen date to the attributes
    2. Recalculate delivery options and fees
  4. displays the delivery method selector with options and prices for the selected day.

It is also necessary to recalculate delivery fees each time the delivery date changes, in the same way as it would if the delivery address changes.

We have already added the datapicker to the checkout using Checkout UI Extension, we have also managed to add the date to cartLineItems.

The question is, how can we get the delivery price to be recalculated after a date is selected/changed?

Thank you

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