POS Discount Technical Reference

This page documents the internal mechanics of how WCPOS handles POS discounts when coupons are applied to an order. For user-facing documentation, see Discounts and Coupons.

How POS Discounts Are Stored

When a cashier changes a line item's price in the POS, the discount data is stored in the _woocommerce_pos_data line item meta as JSON:

{
  "price": "16.00",
  "regular_price": "18.00",
  "tax_status": "taxable"
}

Coupon Interaction Behaviour

When a coupon is applied to an order that contains POS-discounted items:

1. The coupon calculates against the POS-discounted price, not the original price.
2. The order subtotal still reflects the original price for display purposes.
3. When a coupon is removed, the line item returns to the POS-discounted price.

exclude_sale_items Behaviour

POS-discounted items are treated as "on sale" by WooCommerce. Coupons with exclude_sale_items enabled will skip these items, consistent with how WooCommerce treats regular sale prices.

Available Filters

woocommerce_pos_item_is_on_sale

Override whether a POS-discounted item is considered "on sale" for coupon validation purposes.

add_filter('woocommerce_pos_item_is_on_sale', function ($is_on_sale, $product, $item, $pos_data) {
    // Allow coupons with exclude_sale_items to apply to POS-discounted items
    return false;
}, 10, 4);

Parameters:

Parameter	Type	Description
$is_on_sale	bool	Whether the item is considered on sale
$product	WC_Product	The product object
$item	WC_Order_Item_Product	The order line item
$pos_data	array	The POS discount data from _woocommerce_pos_data

Technical Details

• The subtotal filter (woocommerce_order_item_get_subtotal) is temporarily active during coupon recalculation to preserve the original price for display.
• The filter auto-activates on woocommerce_order_applied_coupon (for applying coupons) and via Form_Handler::coupon_action() (for removing coupons).
• The filter auto-deactivates on woocommerce_order_after_calculate_totals.

Known Limitation

Removing a coupon via WP Admin on a POS order may not preserve POS discounts. This is because WooCommerce core does not provide a "before" hook for remove_coupon(), so the subtotal filter cannot be activated in time.