The merged business will have 1,000 staff in Germany, including 68 partners, and 12 offices around the country. This will move Mazars into the top 10 firms in the industry in Germany, creating "an influential player in the national and international scope of Europe's heftiest economy", the company said in a statement.
Mazars has offices in 73 countries, and has doubled its revenues over the past ten years to reach €1.2 billion (US$1.3 billion) in 2015, it said.
Philippe Castagnac, Mazars’ chief executive, said that the merger was prompted by European audit reform, which "is opening new doors for Mazars".
EU member states introduced new rules governing the audit market in 2014, which came into effect in April. European companies must now put their audit requirements out to tender every 10 years. The new rules are intended to increase competition in the sector and strengthen auditors' independence.
"Welcoming Roever Broenner Susat into our firm strengthens our position at the heart of Europe’s first economic power. It’s a smart move," said Castagnac.
The merger is subject to the approval of the German competition authorities.