TALLAHASSEE -- When people in Florida vote by absentee ballot, something very basic is often absent: their signature.

From Key West to Pensacola, thousands of absentee or mail ballots were discarded in the Aug. 14 statewide primary because voters overlooked a requirement that they sign the envelope containing their ballot, even though the instructions conspicuously remind voters to do it.

“It is important that voters complete their own ballot and sign the outside of the absentee envelope themselves,” said Mike Ertel, supervisor of elections in Seminole County near Orlando.

“Each voter needs to sign their own absentee envelope.”

Ertel said voters mistakenly believe that a spouse or family member can sign the envelope on behalf of the voter. They can’t.

Seminole County is smack in the middle of the pivotal I-4 corridor, an area well-stocked with swing voters who could prove decisive in the Nov. 6 presidential election. Millions more Floridians will vote in November than voted in August.

As “no excuse” absentee voting grows in popularity in Florida, elections officials are redoubling their efforts and reminding voters to take their time and fill out the ballot paperwork properly, or risk having their votes not be counted.

Election supervisors emphasize that every vote is carefully scrutinized — including provisional ballots and absentee ballots. Pasco County Supervisor of Elections Brian Corley said an “urban legend” has sprouted up in Florida that provisional ballots are not examined in some cases. They are, always, Corley said.

Absentee ballots are more common, especially in Pinellas County, where Supervisor of Elections Deborah Clark promotes the convenience of at-home voting, with ballot drop-off centers throughout the county.

At the county elections center in Largo, thousands of absentees arrive and depart daily and are categorized using state-of-the-art sorting equipment. Employees seated at computer screens check to be sure that the signature on an absentee ballot matches the same voter’s signature on file.

“There has to be enough of the signature that matches what we have on file, so that we’re comfortable that it’s the same person,” Clark said. “If we feel it’s the voter’s signature, we’ll accept it. If it’s a close call, it goes to the canvassing board.”

Pinellas’ three-member canvassing board was busy in the days after the Aug. 14 primary, when a total of 1,024 questionable absentee ballots were presented to the board, which is composed of a judge, a county commissioner and a staff member of the county elections office.

Ultimately, 302 ballots were rejected, a fraction of the countywide total of 102,625 returned absentees, according to the agency’s website. The other 722 questionable absentee ballots were declared valid and were counted by the canvassing board.

Pinellas’ rejected primary absentee ballots fell mainly into three major categories. Slightly more than half of the rejected mail ballots, 153, lacked a signature, while 85 others were tossed because the signature on the absentee ballot didn’t match the on-file signature of the same voter. An additional 46 absentee ballots were discarded because they were signed by someone other than the voter.

Other counties report similar percentages of rejected absentee ballots, with a variety of different problems that resulted in the votes not being counted.