Totals, taxes and coupons
Line totals and taxes move per unit, rounded so the original keeps the rest. Each coupon’s discount is shared in proportion to the units that moved. The original plus its split orders always equal the amount paid, so reports never count revenue twice.
Stock
Stock is reduced once, when the order is paid. Split orders carry the stock reduction of the units they hold, so completing them changes nothing, and cancelling a split order puts back only its own units.
Shipping and fees
Shipping is never charged twice. It stays on the original order, or the shipping method is also copied to split orders at zero cost for label printing. Fees stay on the original.
Payment and refunds
Split orders are marked paid through the original and carry its payment method and transaction reference. Refunds are issued on the original, which holds the payment, and split orders show a note that says so. Orders with refunds cannot be split.
Emails
Split orders do not send the New order and order received emails again. When a split order ships, WooCommerce sends its usual completed email.