Jay R. Horowitz CPA PC and Miller & Co. LLP, of Manhattan, N.Y., have agreed to merge. The deal will take effect on Jan. 1, 2013.

Midwest regional leader Anders Minkler & Diehl LLP announced plans to add Huber, Ring, Helm & Co., to its practice.

Rich Rotstein LLP has agreed to merge with Collins Barrow Toronto.

Top 100 Firm Sikich LLP added the public accounting and consulting firm, Hill & White LLC. The merger went into effect on December 1.

Marcum Search, a member of the Marcum Group of Companies, has acquired the North American offices of executive search firm Horton International LLC.

WeiserMazars LLP concludes its merger with Creative Health Concepts Inc.

Richmond, Ky.-based accounting firm Baldwin CPAs has merged with Louisville professional services firm Christopher L. Hatcher, CPA.

Montreal-based Richter, formerly RSM Richter Chamberland, merged with Toronto-based SBLR LLP Chartered Accountants.

Walthall, Drake & Wallace LLP added Frank, Seringer & Chaney Inc., of Amherst and Wooster, Ohio, to its practice.

Microsoft Dynamics Master VAR SBS Group has added technology consultant and Dynamics GP, AX, and CRM reseller Enterprise Resources Technology (ERT Group) to its Partner Network.

It looks like U.S. dealmakers may have their hands full with M&A transactions next year.

Seattle-based Top 15 Firm Moss Adams LLP has announced that it will merge with Silicon Valley-based Top 100 Firm Mohler, Nixon & Williams, boosting their combined presence in Northern California. The deal has been approved by partners at both firms, and is due to go into effect on Jan. 1, 2013.

Witt Mares PLC and PBGH LLP have agreed to merge. The deal is expected to take effect on Jan. 1, 2013.

Patrick & Robinson recently acquired the Jacksonville, Fla.-based CPA practice, Petherbridge, Davis & Co. The deal closed in mid-November.

The Los Angeles office of PKF California and the Glendale office of Hutchinson and Bloodgood LLP, have agreed to merge.

Charles “Sandy” Kennedy Jr. joins G.T. Reilly & Co. as vice president and director of tax services.

Top 100 Firm Wipfli LLP and Minnesota-based Eikill & Schilling Ltd., have agreed to pair up.

Doeren Mayhew PC and the Houston-based CPA consulting firm MFR PC agreed to merge. MFR will immediately take on the Doeren Mayhew name.

Payroll and human resource services provider Paychex Inc. has purchased expense report automation product maker ExpenseWire from Rearden Commerce Inc. for an undisclosed sum.

Highlights of firm mergers & acquisitions from the previous month