POS UI extensions 2026-07 uses per-unit fixed-amount line item discounts

POS UI Extensions Now Require Per-Unit Discount Values

Shopify has changed how fixed-amount line item discounts work in POS UI extensions starting with API version 2026-07. Apps must now pass per-unit discount values when using setLineItemDiscount and bulkSetLineItemDiscounts from the Cart API.

Breaking Change in Discount Calculation

In API versions 2026-04 and earlier, developers could pass a total fixed discount amount for an entire line item. Shopify POS automatically converted this total to a per-unit value. With version 2026-07, this automatic conversion no longer happens. The system now interprets the discount value directly as a per-unit amount.

Impact on POS App Development

Developers building or maintaining POS UI extensions need to update their discount calculation logic before migrating to API version 2026-07. Apps that previously calculated discounts as total line item amounts must now divide by quantity to determine the per-unit discount value.

For example, if an app previously applied a $10 discount to a line item with 5 units, it would pass 10 as the discount value. Under the new API version, the app must calculate and pass 2 (10 divided by 5) as the per-unit discount.

This change affects any POS extension that applies fixed-amount discounts to cart line items. Developers should review their discount implementation and test thoroughly with the new API version to ensure discounts calculate correctly at checkout. Apps that don’t update their logic will apply incorrect discount amounts when using API version 2026-07.

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