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The distinctive business postbox for franked mail was introduced in the mid-1990s. Before the advent of such boxes, franked mail could not be posted in a letter box and thus had to be handed in at a post or sorting office unless the business had a visit from the postman. (The reason for this is that ordinary stamped mail would be sent to the sorting office and postmarked, whereas franked mail is already dated by the sender's franking machine.)

Because it is designed for business mail, it is found usually in business parks and industrial estates or in areas of town which are heavily occupied by businesses – and has relatively late final collection times.

It is opened by pulling down the black handle on the sliding opening, and when the final collection of the day is made it will be locked shut and reopened the next weekday morning (including Saturday if the box has a Saturday collection). This is because, as franked mail is dated by the customer rather than at the sorting office, it must be posted on the same day as the date indicated on the franked impression. By accepting later items which would not be collected till the following day, it would give the false impression that Royal Mail had taken a day longer to deliver the item.