The New York City Board of Elections has a proofreading problem — and even small mistakes are turning out to be costly.

The board was forced to spend more than $200,000 in overnight postage last month to send corrected absentee ballots for the coming presidential primary, after it discovered an error in the Spanish version of the ballot.

The mistake was discovered around the same time the board realized it had made another error: A recent notice sent to 60,000 newly registered voters included the wrong date for a Sept. 13 primary election for state and local offices. The board then mailed out a correction that may have inadvertently confused voters about the date of the higher-profile presidential primary on April 19.

Those incidents follow a major mistake in the Chinese translation that appeared on ballots for the state’s election in November 2013, which led to the firing of one translator and the resignation of another.