SALEM — The Independent Party of Oregon wants you to know that if you’re registered to vote in Oregon, but don’t belong to a political party, you can still cast a ballot in their primary May 15.

You’ll need to ask the Secretary of State for that ballot, though.

The party says Secretary of State Dennis Richardson has decided not to send what IPO leaders say is a routine mailed reminder to non-affiliated voters this year.

According to the party, the Secretary of State’s Office sent those mailings in 1992, 2000, 2012 and 2016.

It’s not apparent why the reminders won’t be sent in 2018 — Secretary of State Dennis Richardson’s office did not immediately respond to a request for comment Wednesday afternoon.

Even though the notice won’t be sent out this year, non-affiliated Oregonians can request a ballot online at: http://sos.oregon.gov/voting/Documents/voters-not-registered-with-party.pdf. Another, shorter url set up by the party is http://indparty.com/getballot.

The notice will also be in the voters’ pamphlet. But the deadline to request an IPO ballot is April 24, and the party is concerned that some voters will not receive their voters’ pamphlets by then.

While non-affiliated voters can email, mail, fax or submit a request for an IPO ballot to their local county elections office in person, the offices will need to have it in hand by 5 p.m. April 24, so people mailing their requests will need to plan ahead.

The Democratic and Republican primaries will be open only to members of those parties.

“Because Oregon allows major parties to close their primaries to non-members, none of those voters will have a chance to choose which candidates will appear in partisan races on the November ballot,” said Sal Peralta, secretary of the Independent Party of Oregon, in a prepared statement. “IPO has opened its primary to all non-affiliated voters, but they cannot participate if they do not know about it and affirmatively request the IPO ballot from their county election offices.”

IPO co-chair Dan Meek called the ballot-requesting system “convoluted,” and argued that a simpler and less expensive process would be to send all non-affiliated voters IPO primary ballots.

“It would save money and time if the Secretary of State merely sent the IPO primary ballot to all non-affiliated voters, along with their ballots for non-partisan races and ballot measures,” Meek said in a statement.

Since Oregon passed and implemented an automatic voter registration law — referred to as “Motor Voter” — the number of voters who aren’t registered as members of a particular party has multiplied.

As of February, there are about 820,370 non-affiliated voters in the state, according to Secretary of State data. That’s about 30.9 percent of Oregon’s registered voters — compared to 436,046, or about 22 percent of all Oregon voters, in February 2008.