A reported break-in at the Centereach post office may have included the theft of about two dozen checks sent to the Brookhaven Town tax receiver's office, officials said Wednesday. Alarmed taxpayers called Brookhaven Town Receiver of Taxes Louis Marcoccia this week after receiving postcards from the town alerting them that they had failed to pay their property tax bills, he said in a telephone interview. Taxes were due Monday, he said.