A Brooklyn building owner claims the city has unfairly quintupled its tax rate.

Two Chopsticks LLC, owners of a Coney Island Avenue building in Prospect Park South, say they’re on the hook for $30,000 in taxes instead of a manageable $6,000 because of a city clerical error.

The owners, who sank more than $200,000 into the three-story property after they bought it a couple of years ago, are suing the city in Brooklyn Supreme Court.

The city Finance Department did not return a message.