A packing slip is the contents list you put inside the box so the buyer can check the order against what arrived. It carries items and quantities, never money, and no carrier scan ever reads it.
The label prices and moves the parcel. The slip tells a human what should be in it.
Think of it as a note to the person holding a box cutter. It repeats the order back to them so they can check the contents without hunting through email, and it tells them who to contact if something is short or wrong.
What does not belong: prices, payment method, card digits or tax lines. That set belongs on the invoice, which is a financial record for you and the buyer. Gift orders are the clearest case for keeping the two apart, since the recipient should see the contents list and not the amount paid.
Three documents get used interchangeably in seller forums, and they do genuinely different jobs.
For a domestic parcel the document that gets scanned is the label on the outside, and the label is what the price is built from. Nothing inside the carton changes the rate. That is why a packing slip is a customer-service tool rather than a shipping requirement.
Six shipments that turn up constantly in a one-person shop, priced on the same lane on the same day so the comparison is honest. Each price is the whole amount collected at checkout with SMKlog inside it.
| Parcel | Packed box | Weight | Cheapest quoted | Carrier and service |
|---|---|---|---|---|
| Paperback book | 8 x 5 x 1.5 in | 1 lb | $9.91 | USPS Ground Advantage |
| T-shirt in a poly mailer | 12 x 9 x 1 in | 0.7 lb | $8.86 | USPS Ground Advantage |
| Ceramic mug in a box | 6 x 5 x 5 in | 2 lb | $8.48 | USPS Ground Advantage |
| Phone in a padded envelope | 9 x 6 x 1.5 in | 0.6 lb | $8.86 | USPS Ground Advantage |
| Carton of goods | 12 x 12 x 12 in | 15 lb | $17.01 | USPS Ground Advantage |
| Larger carton | 20 x 16 x 12 in | 25 lb | $28.77 | FedEx Ground Economy |
Two rows are worth staring at. The mug at 2 lb quoted less than the book at 1 lb, and the 25 lb carton cost more than three times the mug for eight times the load. Weight bands and box sizes interact in ways a printed slip will never reveal, which is the whole argument for quoting per order instead of memorising a number.
Face up, on top of the packing material, so it is the first thing seen. Sliding it down the side of the carton means it gets binned with the void fill. Some sellers tape it to the inside of the flap, which works fine and survives an aggressive unboxing.
Adhesive document pouches exist for international customs paperwork that has to be readable without opening the box. For a domestic order the slip is for the buyer, so plain paper inside the carton does the job at no cost.
A second copy with a tick box for the reason turns a vague complaint into a usable record. It costs a sheet of paper and saves a chain of messages.
No prices anywhere on it. A word processor, a spreadsheet or a plain text file all produce this in less time than it takes to find a template site, and the layout is yours to keep consistent across every order you send.
It is an itemised list of what is inside a shipment, printed for the person who opens the box. Order number, ship-to name, and each line item with its quantity. Amounts, tax and payment details are left off, which is the whole distinction between a slip and an invoice.
No carrier requires one on a domestic parcel, and no rate depends on it. Some marketplaces and wholesale buyers ask for one in their own terms, so read those. Otherwise it is a service choice that costs you a sheet of paper and prevents a category of buyer messages.
A packing slip answers what is in the box. An invoice answers what was owed and whether it was paid. Gift orders are the clearest reason to keep them separate, since the recipient should not be handed the amount the buyer spent.
Face up on top of the packing material, so it is seen before anything is unwrapped. A commercial invoice for a cross-border shipment is the one that rides in an external pouch, and we do not sell international labels, so that case never comes up here.