Custom Shopify Discount Functions

Shopify’s built-in discounts cover a percentage off, a fixed amount, or a simple buy X get Y. The moment a promotion depends on tiers across mixed products, on who the customer is, or on what else is in the cart, you need a Discount Function: custom discount logic that runs inside Shopify’s own checkout.

What a Discount Function can do

One Function can discount three things at once: the products in the cart, the order subtotal and shipping. It can apply automatically or behind a code, and it reads the cart, the customer and your own metafields to decide what applies.

• Tiered and volume pricing. Spend $100 and save 10%, spend $200 and save 15%. Buy three from a collection and get the cheapest free.
• Buy X get Y and gifts with purchase, with the exclusions and caps your promotion needs.
• Shipping discounts by cart value, product, customer tag or destination.
• Customer-specific pricing for VIPs, members or wholesale buyers.
• Exclusions, like keeping engraved or already-reduced items out of a sale.

Built to combine the way you intend

Discount Functions run side by side, and Shopify decides how their results stack using the combination settings on each discount. We plan that up front, so a sitewide sale, a loyalty offer and free shipping interact exactly the way you expect, with no surprise double discounts.

Settings your team controls

Hard-coded thresholds were the weak point of Shopify Scripts. We keep tiers, percentages and eligible products in settings your team can edit in the admin, so the next promotion does not need a developer.

Replacing a line item Script?

Shopify Scripts stopped running on June 30, 2026, and most line item Scripts were discount logic. A Discount Function is where that logic lives now. See our Scripts to Functions migration service for how we rebuild it, and custom bundles and add-ons if your offer is really a bundle.