An American citizen votes during by mail at the U.S. Embassy in Buenos Aires on Oct. 8, 2008. Getty Images

In a presidential election as competitive as this one, you don't want to risk any complications with your precious vote. Be careful: If you're voting by mail, something as simple as postage could impact your ability to do your civic duty.

"The number of ballots mailed back to election officials with insufficient postage is on the rise," the Unites States Postal Office writes on its website. "Each election cycle presents a different set of parameters for ballot creation and for the size and weight of the return mailpiece. As a result, many voters do not know the correct amount of postage required to return their ballot by mail."

2016 is no exception. People are already flooding social media with questions about how many stamps they need, why they have to pay to vote and what happens if they don't use the right postage, according to Snopes. Here's what you need to know.

Depending on where you are, you may need two stamps. If your absentee ballot says "extra postage required" or "apply first-class mail postage," a single regular $0.47 stamp might not cut it. Whereas usually you can mail about four pages with one stamp in a standard envelope, absentee ballots often weigh more, according to NPR. The more pages there are, the more you need to spend to vote.

That's the case in San Diego County, California, where it costs $0.67 to mail your ballot because it's two pages. In Arapahoe County, Colorado and Snohomish County, Washington, it costs $0.68.

Your absentee ballot should include instructions on how much postage you need. Make sure to read carefully before sending back your ballot. If you can, call and confirm with your local supervisor of elections office before putting your papers in the mail. Or just go to the post office and ask.

That might seem like a lot of work, but authorities sometimes make mistakes. For example, this month in Franklin County, Ohio, officials discovered they'd accidentally printed the wrong amount of postage on their absentee ballots, the Columbus Dispatch reported.

If you don't put the right amount of postage on, your ballot will still (probably) be counted. In Missoula County, Montana, for example, election official Vickie Zeier told KECI that she'll get ballots whether they're properly stamped or not. "The post office will send it to us with postage due and we'll accept the ballot," Zeier added.

The U.S. Postal Service itself wrote on its website in 2014 that "short-paid and unpaid absentee balloting materials must never be returned to the voter for additional postage." The election office will pay for the postage at a later time.

To be safe, though, you may want to use multiple stamps.