Postal Service (USPS) has also said they would deliver ballots even if there was insufficient or unpaid postage.
While Americans should pay for postage where required, at the time, USPS said it was their policy to deliver return ballots regardless of insufficient or unpaid postage.
It is true that in Ohio, voters are responsible for paying for their mail-in ballot’s postage (here).
In cases where a voter sends a ballot with insufficient postage, the cost of such missing postage would likely be absorbed by the relevant elections board.
Postal Service has said they deliver ballots even if they have insufficient or unpaid postage.