Thousands of Rock County residents recently received mailings urging them to register to vote, but some of them are already registered.

A nonprofit organization in Washington, D.C., called Voter Participation Center says it sent the registration mailings to 11,100 residents of Rock County and 4,400 in Walworth County, and it plans two more mailings this year.

The organization says it sent 401,124 of the reminders statewide.

The mailings include a registration form and a postage-paid envelope addressed to the local municipal clerk.

“The Voter Participation Center is a non-profit, non-partisan organization dedicated to increasing voter registration in the United States among young people, people of color and unmarried women,” according to its website.

“What we find is a lot of people aren’t sure about their status and sometimes think they’re registered and then find out they’re not,” said the organization’s CEO, Jessica Barba Brown. “We really think this election and all elections really are too important to have people not have their voices heard.”

Rock County Clerk Lisa Tollefson said a handful of Janesville residents contacted her office about the mailings, and at least four were already registered. One was not. The city of Beloit clerk has reported similar contacts.

People who receive such mailings should check first to see if they are already registered, Tollefson said.

The mailing includes a copy of Wisconsin’s registration form, but it’s an older version of the form that doesn’t highlight the fact that proof of residency is required, Tollefson said.

The mailing’s cover letter does state, in bold type, that proof of residence is required. The letter also notes that registration status can be checked at the myvote.wi.gov website.

If people send the forms to their municipal clerks without proof of residency, “the clerks will have to send you a letter saying we need more information,” Tollefson said.

Tollefson noted the next election is the Feb. 18 spring primary. The last day to register online for that election is Wednesday, Jan. 29, but residents can register at their local clerk’s office through the Friday before the election, Feb. 14. And voters can register at the polls on Election Day.

Proof of residency could be a driver’s license with a current address or even a utility bill that includes the person’s name and address.

Online registration begins again Feb. 19.

The state Elections Commission sent an alert in October 2018 about similar mailings from the Center for Voter Information, which is a sister organization to Voter Participation Center.

Other organizations similarly intent on getting people to vote might send similar mailings in the year ahead, Tollefson said.

Barba Brown said her organization has been “incredibly successful,” registering 121,000 Wisconsinites since beginning operations 16 years ago. The mailings this year will be the largest in the organization’s history.

The group compares Wisconsin’s voter rolls to other public documents to find out who might have moved since the last election. Voter registrations must be updated when a person moves.

The process includes 22 data quality steps to make sure they are as accurate as possible, “but since this is such a large mailing, there can be errors from time to time,” Barba Brown said, adding that the error rate is less than 1%.

People in the organization’s target group move more often than average, and experience shows they need multiple reminders before they register, Barba Brown said.

No matter what happens, voters who get to the polls this year can register at the polls, although they might encounter lines, especially in November.

This year’s elections are the Feb. 18 spring primaries; the nonpartisan spring elections April 7, which also include the presidential preference primaries; fall primaries Aug. 11; and Nov. 3, which includes elections for state offices, the House of Representatives and president.