Post-paid and Prepaid

Post-paid adverb - Having the postage paid by the sender.

Prepaid and post-paid are semantically related. In some cases you can use "Prepaid" instead an adjective phrase "Post-paid".

Prepaid adjective - Used especially of mail; paid in advance.

Post-paid and prepaid are semantically related. Sometimes you can replace phrase "Post-paid" with "Prepaid", this terms are similar.