A new definition will be introduced for the type of business that can bring complaints to the FOS in line with European Union law.
Currently private individuals, small businesses with an annual turnover of less than £1m, charities with a yearly income of under £1m and trusts with net assets under £1m can make use of the scheme.
But under the new rules to come into force on November 1, only private individuals and micro-enterprises can bring a complaint to the ombudsman.
A micro-enterprise is defined as a company with an annual turnover of under €2m, or approximately £1.7m, and fewer than 10 employees.
The latest issue of Ombudsman News states: “The proportion of complaints referred to us by smaller businesses increased slightly last year from 2 per cent to 3 per cent of all cases.
“The small rise in complaints brought by businesses may reflect our outreach work in this area, which has included liaising with smaller-business trade associations and networks, taking part in events such as Business Start-Up shows and arranging targeted coverage in specialist business-to-business publications.”