Cedilla Systems, the Manchester reseller, is selling itself to a Dutch dealership.
Watermark, which dubs itself the leading Microsoft Dynamics partner in Europe, aims to complete the takeover in June.
Manchester-based Cedilla is best known for supplying REgenerist software based on Microsoft Dynamics NAV.
It had a turnover of £2.7m in 2006 and hires around 30 staff.
Mike Dickson, managing director of Cedilla, said that the announcement "will enable us to provide a broader range of Microsoft solutions and services to our customers. In addition we will able to serve larger, and international, companies in our target vertical markets."
Both companies supply software for the the waste management sector as well as the professional service industry.
Speaking about the acquisition, Thomas Ajspur, sales director of Watermark – said one of the goals "is to become the leading Microsoft Dynamics partner in the UK."
Watermark was itself acquired last December, by another Dutch Microsoft dealer, called Qurius. ®