PrimeCommerce
PrimeCommerce books the parcel with your courier from the order itself. It keeps the consignment and tracking number, takes the stock off the shelf in the same step, and follows the parcel until its cash is matched. Use your own courier accounts, or ship on PrimeHat's.

On Free every order ships with PrimeHat. Grow and up connect as many as you need.
Who collects the cash and what each way needs: Shipping on PrimeHat.

The courier sends its updates as they happen, and PrimeCommerce also asks: every 10 minutes while a parcel is new, every 30 minutes after that. Each update shows on the order. The buyer follows the parcel on Track Order, with a plain status such as In transit, Out for delivery or Delivered, never the courier's raw wording.
On your own courier account, a delivered cash-on-delivery parcel becomes money the courier owes you. To check what the courier pays:
The Earnings page shows each courier's figures: delivered, collected, settled, and still owed.

Connect a courier account in Settings → Couriers with the keys from its merchant panel. They are tested with the courier before they're saved, stored encrypted, and never shown back.
Rules that choose the courier for each parcel. Follow it on the changelog.
No. With Ship with PrimeHat, parcels go out on PrimeHat's courier accounts once our team has verified your pickup address. If you want your own rates, connect your own account in Settings → Couriers. See Shipping on PrimeHat.
The parcel is on PrimeHat's courier account, so the courier pays the cash it collects to PrimeHat. For what happens next, see Shipping on PrimeHat.
Nothing is written off by itself. That parcel simply isn't settled: it stays in what the courier still owes you on the Earnings page until a later statement pays it. A statement line that matches none of your delivered parcels shows as unmatched in the dry run.