Once a pick list is picked, two things are left: get the goods out of the building, and handle what comes back. Both live on the warehouse floor, and both are careful about one thing — what is actually in stock.
Packing
Packing shows every list whose lines have all been picked. Open a package for it, weigh the box, and pack it. A big order can be several packages; each is numbered, and its slip says which of how many.
The packing slip is printable and carries no prices. It travels with the goods, and the person who opens the box is not the person who pays — the bill goes to the customer separately.
Dispatch
Dispatching a package says the goods have left. It marks the list dispatched and releases the stock the pick was holding — not because the stock came back, but because it has gone, so there is nothing left to hold.
Dispatch does not move stock. The bill or the stock transfer the goods are for is what moves it, and that has already happened or is about to. If you want a courier to collect, book the parcel from Parcels against your own courier account.
Taking a return back
A return handed over the counter belongs on the till's return screen — the cashier is looking at the goods while the customer stands there. A parcel that arrives in the post is different: nobody has seen it yet. Returns makes that inspection explicit.
Receive the return, naming the original bill if you have it. Then inspect each item: what condition it is in — sellable, damaged, or a reject that was never yours — and what happens to it: back on the shelf, scrapped, or sent for repair. A damaged item cannot be put back on the shelf. That is refused rather than warned about, because a damaged item quietly restocked is exactly what an inspection exists to prevent.
What posting does
Posting issues a credit note against the original bill — the same document the till issues, so it posts to your books and reaches GSTR-1 the same way. The dispositions decide the stock: only the items you marked sellable and put back come back into stock. Scrap and repair lines credit the customer and put nothing on a shelf, which is the honest outcome — the customer's money goes back, and the goods are gone.
A credit note has to be against something, so a return with no bill attached cannot be posted until one is named. Cancelling a posted return cancels its credit note rather than deleting it, so the trail stays readable afterwards.