If you intend to vote in next year's presidential primary and are not affiliated with a political party or want to change your affiliation, you must register by Friday.
Wendy Weiser of The Brennan Center for Justice says it's an unexpected deadline for many citizens.
"It creates a lot of problems for people who want to vote in a primary and are shut out because they miss a deadline they had no reason to think was so far in advance," she said.
Weiser said in the 2008 presidential primary, many voters were turned away from their polling station for not officially registering with a political party.
The Board of Elections offices in lower Manhattan will be open until midnight on Friday to receive registrations.