The company also noted those who have already tendered shares can withdraw them by 12:01 am EDT on October 4 by following instruction in the TRC offer documents.

The offer comes at a time when rival Automatic Data Processing has been facing a proxy fight from investor Bill Ackman, whose Pershing Square Capital Management had been seeking control of the that company.

TRC says the move is only for investment purposes and it has no intent to influence the board of directors or management. In its SEC filing, Paychex wrote, "Nonetheless, Paychex does not endorse this unsolicited mini-tender offer and recommends that shareholders do not tender their shares in response to the offer."

Paychex says the purchase pricing is 4.07 percent lower than the closing price of Paychex shares on September 1, the last trading day before the mini-tender offer began. It also said the offer "is subject to a number of conditions."

Bob Scott

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Bob Scott has provided information to the tax and accounting community since 1991, first as technology editor of Accounting Today, and from 1997 through 2009 as editor of its sister publication, Accounting Technology. He is known throughout the industry for his depth of knowledge and for his high journalistic standards.  Scott has made frequent appearances as a speaker, moderator and panelist and events serving tax and accounting professionals. He  has a strong background in computer journalism as an editor with two former trade publications, Computer+Software News and MIS Week and spent several years with weekly and daily newspapers in Morris County New Jersey prior to that.  A graduate of Indiana University with a degree in journalism, Bob is a native of Madison, Ind