Peterson Sullivan LLP expanded its Seattle practice with the addition of Davenny & Associates PS.

Sikich LLP has merged with Achieve Consulting, a supply chain consulting firm based in Warrenville, Ill.

Top 100 Firm, Kahn, Litwin, Renza & Co. Ltd., has agreed to merge with Fay & Associates.

Top 100 Firm, CliftonLarsonAllen LLP has merged with the Racine, Wis.-based CPA firm Jenkins & Vojtisek SC.

Global tax services firm Ryan LLC has acquired the Property Tax Services business from Thomson Reuters for an undisclosed amount.

CBIZ, Inc. has acquired “certain” assets of Diversified Industries, Inc. for an undisclosed amount.

CBIZ, Inc. has completed an acquisition of the non-attest assets of PHBV Partners LLP, the government health care practice and separate legal entity of CliftonLarsonAllen.

Regional Leader BeachFleischman PC and Phoenix-based CPA firm Taylor, Duffy & Associates PC have merged, effective January 1.

Our panel of experts explains the future of firm combinations in 2013

Firm mergers and acquisitions from the previous month

The U.S. Justice Department opened an investigation relating to Autonomy Corp. after Hewlett- Packard Co. accused the software company of misrepresenting its performance before being bought last year.

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.