The agency filed an operating loss of £1.7m for the 18 months ending December 2010 at Companies House, compared to an operating profit of £550,000 for the 12 months ending June 2009.
Its turnover was £43m for the 18-month period compared to £35.4m for the year ending June 2009, while gross profit was £12.7m compared to £8.5m.
Grass Roots finance director Graham Corfield said extending the financial period was a group decision to align the company with clients whose financial years end in December.
"We have been through a rough recession and the bulk of the losses were in the July to December 2009 period when lots of clients held back and cut budget," said Corfield. "In 2011 a return to profitability will happen."
The agency is currently trading ahead of its budget for the year to date, and does not plan to reduce current staff numbers, he added.
In a statement filed at Companies House Grass Roots Eventcom said it will now focus on delivering added value, better use of technology and a more flexible approach to staffing to maximise reaction to shorter lead times.
In C&IT's State of the Industry report, Grass Roots’ overall results were forecast at £49.2m total turnover for the year ended December 2010, with pre-tax profit of £1.6m. These figures included the company’s other divisions which include delegate management and venue procurement.