Royal Mail requires their account holders to print a Sales Order Summary for your day's shipments. This is how Royal Mail invoices your courier fees to your account’s.
In ShipStation, you can generate your Sales Order Summary in the Shipments > End of Day window. Keep in mind, for Royal Mail shipments, this is a REQUIRED step.
To generate this Sales Order Summary, click on the Shipments tab.
On the Shipments page, click the End of Day section in the lefthand sidebar.
In the window that appears, you will see your shipment count for the current date.
On the line for Royal Mail, click Close Shipments.
*If you need to go back and close a previous date's shipments as well, you can! Just select a different date from the calendar drop-down.
Click Close All, or select the desired shipments and click Close Selected.
This will transmit your shipment information to Royal Mail electronically so you can be properly invoiced. When you drop off your day's shipments, be sure to also include the printed form.
For more information on using Royal Mail in ShipStation, please read the article How do I use Royal Mail within ShipStation?