Starting with API version 2026-04, Tax Partner Apps can now receive custom cart line item properties in tax calculation requests. Merchants can configure properties like tokens, personalization details, or gift wrap options on individual line items, and tax apps can specify which property keys they want to receive. This enhancement ensures that only the requested property data is included in calculation requests, keeping payloads efficient and focused.
Tax calculations often depend on nuanced product details beyond basic line item information. By gaining access to custom cart line properties, tax apps can now make more accurate, context-aware tax determinations—especially for complex scenarios involving personalization fees, gift wrapping, or custom product configurations. This update bridges a critical gap that previously limited tax apps' visibility into merchant-specific line item customizations.
If you're building or maintaining a Tax Partner App, GetShopifyToken simplifies secure authentication to Shopify's Admin API. Quickly generate access tokens to test and deploy your tax calculation updates without authentication overhead.