A packing slip is a small document, but a mistake on it lands directly in front of the customer the moment they open the box — which makes even minor errors here more visible than similar mistakes buried in back-office paperwork.
Quantity mismatches
Listing 3 units when only 2 are in the box (or vice versa) is one of the fastest ways to generate a support ticket — always double-check quantities against what's actually packed, not just what the order system says was ordered.
Vague item descriptions
"Item A" or an internal SKU code with no readable description leaves the customer unable to identify what they're looking at, especially for orders with multiple similar products.
Missing items not noted as backordered
If part of an order is genuinely out of stock and shipping separately later, the packing slip should say so explicitly — a customer who receives a partial shipment with no explanation reasonably assumes something is missing or wrong.
Wrong recipient address on the slip itself
An outdated or mismatched address on the internal packing slip (separate from the shipping label) can cause confusion, especially for gift orders being reviewed by someone other than the buyer.
Inconsistent formatting across orders
A packing slip that looks different every time (different layout, missing fields some orders have and others don't) looks unprofessional and makes your own quality control harder — a consistent template used every time reduces errors on both sides.