The IT business, whose services run from telecoms to cloud solutions, said accounts due in February will show losses before tax will have deepened compared with the £1.12 million booked the year before.
It expects earnings before interest, tax, depreciation and amortisation (EBITDA) to have deteriorated on the £284,554 recorded in 2012.
AIM-listed Pinnacle, which rebuffed a £6.7m takeover bid from London-based Coms in September, said the "disappointing" results will also confirm a fall in revenue, as previously noted at its interim announcement in June.
It said turnover will come in at around £10.1m, down on the previous year's £12.7m. The group pinned the results on the absence of high-profile events over the period compared to 2012.
That year had seen Pinnacle provide internet and telecoms solutions to the BBC during the Olympics, Paralympics, and the Queen's Diamond Jubilee celebrations, building on previous contracts for events such as the Royal Wedding in 2011.
It said its 2013 figures were also hit by the poor performance of RMS IT Security, the Stoke-on-Trent-based security software provider it had acquired for more than £460,000 in October 2011.
That deal, made through its Pinnacle Cloud Solutions subsidiary, had brought the firm a further 1700 customers, many in the public sector.
In spite of its downbeat assessment of 2013, Pinnacle said the group was trading close to break-even in its current financial year on an EBITDA basis.
It said a strategic review put in place after announcing its interim results on March 30 has seen it take "robust actions to reduce ongoing costs in recent months".
Mr Bonner, who was nominated in last year's Entrepreneurial Exchange Awards, was unavailable for comment yesterday.
But he said in a statement: "I am pleased to report that the group is now trading close to EBITDA break-even on a monthly basis. However, I have decided that after 15 years since I started Pinnacle, the time is now right to seek my successor. I am hopeful that we can soon appoint a new chief executive who will help us achieve our objectives and I look forward to ensuring a smooth transition in the best interests of our customers, staff and all other stakeholders."
The company expects to announce its full-year results for the year to September 30 in February, adding that it will update the market on the search for Mr Bonner's successor in due course.
Mr Bonner moved into the telecommunications industry following stints in insurance and private healthcare sales in 1996.
He developed a firm that sold telecommunications products on behalf of suppliers, which was bought by a rival based in Kent, before acquiring the then loss-making Glen Group (now Pinnacle) in 2007. Since then he has developed a new service offering which has led to contracts at major events, and used acquisitions to increase its customer base.
Mr Bonner's departure comes after Dr James Dodd replaced former Thus chief executive Bill Allan as chairman at Pinnacle at the start of the year.
Shares in Pinnacle closed down 1.75p at 17.25p.