Payroll software firm Paychex Inc. agreed to buy privately held SurePayroll Inc. for an undisclosed sum.

Rochester, N.Y.-based Paychex provides a full menu of services for small to medium-size businesses such as payroll, human resources and employee benefits outsourcing. Meanwhile, SurePayroll, which has about 30,000 small business customers, provides online payroll services through banking partners including  Citibank, Harris Bank and SunTrust Bank.
The combined companies say they hope to further tap a growing business of customers who have manual payroll and covert it to online.

“We are excited to have SurePayroll join the Paychex family,” said Paychex Chief Executive Martin Mucci. “This acquisition helps Paychex expand further into a new segment of the online market for small business — a fast-growing part of the market that we believe will continue to thrive.”