What meter sales must be reported using PS Form 3602 - PO?

The correct choice, which is postage, is essential to report using PS Form 3602 - PO because this form is specifically designed to capture all meter sales for postage at post office locations. Meter sales refer to postage that is printed from mailing meters, which are used to automate the application of postage on mail pieces.

This reporting is critical for ensuring accurate accounting of postage used and maintaining financial integrity in postal operations. Postage is a core service provided by the postal authority and tracking meter sales of postage helps in monitoring revenue and production levels.

Other mail types like registered mail, express mail, and parcel select have specific reporting requirements and are typically accounted for using different forms or tracking systems, which is likely why they do not fall under the PS Form 3602 - PO purview.