Requirements
Any paid Annual plan in Send To Many, or the monthly Growth tier or higher
Development resources to adding one or two new API endpoints to an existing custom shipping / delivery app
Understanding of Send To Many's Date and Rate API
Many gifting merchants have complex date and availability requirements for specific products, locations and time periods. Some are able to use third party apps such as Zapiet or Bird to power this functionality in their Shopify checkout experience. For those merchants, Send To Many can integrate directly with those apps to offer the same options in multi-recipient checkout that they already offer in the standard Shopify single-address checkout.
Other merchants have developed custom apps to support their specific shipping-date and shipping-rate logic. Send To Many's Date and Rate API makes it possible for merchants to adapt their existing functionality to the multi-recipient checkout experience.
Many merchants rely on custom apps to control:
which delivery or ship dates are available
which shipping rates apply for a given address, product mix, and date
Those apps may be implemented either:
as Shopify Carrier Services (returning rates directly to Shopify), or
as Checkout Functions / Extensions with custom logic that isn’t exposed through Shopify’s rate-request flow
Send to Many's Dates and Rates API endpoints let those existing apps power multi-recipient checkout and bulk order uploads without re-implementing their logic.
Here's how the date and rate selection process works in Send To Many. For each recipient:
Send to Many asks the merchant’s app which dates are valid based on the address and products set for each recipient
shows only those dates in a picker
then determines the available shipping rates for the selected date
defaults to the first returned rate, while allowing the buyer to change it
and then includes the selected date and shipping rate on each resulting child order
Technical overview: two integration patterns
Merchants only need to implement the pieces that match how their shipping app already works.
Pattern 1: Date-aware rates via Shopify Carrier Services
Best fit for:
Custom shipping apps that already accept a shipping date selection and return valid rates through Shopify’s Carrier Services API, where rate logic can account for address, products, and selected ship or delivery date.
How Send to Many integrates:
Delivery Availability endpoint
Send to Many calls the Delivery Availability endpoint with:
recipient address
selected products
The app returns:
which dates are allowed or blocked or an error message if no dates are available
optional custom order properties (tags, notes, line item attributes, etc.)
Send to Many uses this response to render a constrained date picker.
Shipping rates
After a date is selected, Send to Many requests rates from Shopify.
Shopify calls the merchant’s Carrier Service, which returns date-aware rates.
Send to Many displays the rates exactly as Shopify returns them.
This pattern allows merchants to reuse their existing Shopify rate infrastructure, with the addition of a single endpoint exposed to Send To Many.
Pattern 2: Rates calculated outside Shopify checkout functions
Best fit for:
Shipping apps implemented using Checkout Functions or other custom logic where:
valid dates can be calculated independently
but shipping rates cannot be returned through Shopify’s Carrier Services API
How Send to Many integrates:
Delivery Availability endpoint
Send to Many requests valid delivery dates using the same inputs:
address
products
The app returns date picker configuration and optional order properties.
Shipping Rates endpoint
Once a delivery date is selected, Send to Many calls the Shipping Rates endpoint.
The request includes:
address
products
selected delivery date
The app returns a list of valid rates for that specific date.
Rate selection
Send to Many displays the returned rates in order
Defaults to the first rate
Allows the buyer to change the selection
This pattern gives merchants full control over date-specific pricing logic without relying on Shopify’s rate-request pipeline.
Contact us to explore your custom date and rate integration!