Suffolk County National Bank is expected to begin laying off 76 back-office workers in Riverhead in January.

The reason for the layoffs is that Suffolk Bancorp, the bank’s Riverhead-based holding company, is being acquired by Connecticut-based People’s United Financial Inc., according to a WARN notice posted on the state Department of Labor’s website.

The filing states that 65 employees at its headquarters on 4 W. Second St. and 11 workers at 206 Griffing Ave. will lose their jobs during a two-week period starting Jan. 26. The workers are not represented by a union, according to the notice, which was filed on Friday.

The layoffs will affect back-office and administrative workers in areas such as information technology, which is based in the Griffing Avenue building, as well as finance and operations, Brian Finneran, Suffolk Bancorp’s chief financial officer, said in an interview. The jobs being eliminated are “duplicative of positions that they already have” at People’s, Finneran said.

“The good news here is that People’s has agreed to give priority” to Suffolk Bancorp employees who apply for jobs with the Connecticut bank, Finneran said.

Last month, Suffolk Bancorp shareholders approved the proposed sale to People’s United. The all-stock deal is valued at about $402 million, and is awaiting regulatory approval.

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Finneran said he expects regulators to make their decisions by December or January. The Suffolk County National Bank branches are expected to take on the People’s United name after the merger closes, he said.

Under WARN, New York’s Worker Adjustment and Retraining Notification Act, companies with at least 50 full-time employees must give them at least a 90-day notice of a mass layoff or closing.