A numberof Ireland's leading domestic waste disposal companies have adopted offshore ownership structures - a move which has hidden their profits from scrutiny.
Companies in the Isle of Man, Jersey and the British Virgin Islands are being used to keep earnings details from competitors and the general public.
Several firms have also changed their status from limited to unlimited, which means they don't have to disclose their accounts in Ireland.
The structures, which are entirely lawful, make it impossible to tell how much companies are making from the multi-million euro domestic waste market or how much tax they are paying.
It also means that changes in the beneficial ownership of the firms can be kept secret.
The City Bin Co was among the first to start the trend when it re-registered as an unlimited company in 2006.
The company, founded by businessmen Glen Ward and Gene Browne, was initially based in Galway, but it has since expanded operations to Dublin, where its depot was targeted in an arson attack in 2012.
Its last set of published accounts, for the 12 months to July 2006, showed a profit for that year of €1.7m.
The firm's shares are held by an unlimited company in Jersey and a Galway-based unlimited company, which is ultimately owned by two other companies in Jersey.
A spokesman told the Irish Independent it paid all of its taxes in Ireland.
"The City Bin Co uses the unlimited status to keep our detailed accounts undisclosed from our competitors. This is common practise for hundreds of companies in Ireland and also for many in our sector," he said.
Oxigen followed suit in 2009 when it too re-registered as an unlimited entity.
The firm, owned by the Doyle family from Dunleer, Co Louth, operates waste disposal services in Cavan, Monaghan Kildare, Louth, Meath, Westmeath, Laois, Offaly and Waterford.
The last set of publicly available accounts for Oxigen Environmental Ltd showed a €13.3m profit for 2008. Its six directors at the time were paid €1.25m between them for the year and had €778,218 paid into their pensions.
The shares in the company are now ultimately held by entities registered in Douglas in the Isle of Man.
Greyhound, owned by brothers Brian and Michael Buckley, re-registered as an unlimited company and moved its shares to an Isle of Man company in 2010. It took over Dublin City Council's waste operation in 2012.
Panda Waste, run by Navan-based businessmen Noel and Eamon Waters, adopted unlimited status two years ago.
The company operates across Dublin, Louth and Meath.
It is controlled by an entity called Adnap Holdings, the shares in which are held by companies with post office box addresses in the Isle of Man.
In the last set of accounts, it filed as a limited company, Adnap recorded a turnover of €60.2m and profits of €3.5m for 2011.
A spokesman for Greyhound said the structures were "very much about competition".
"Any kind of leaked information could have a major impact on a particular area where you are collecting and give competitors an insight," he said.
"As far as Greyhound is concerned, it is purely for competitive reasons. We pay all our taxes in Ireland. There is no tax being paid offshore or anything like that."
Mallow-based Country Clean recycling re-registered as an unlimited company.
Run by husband and wife team David and Mary O'Regan, the company shed its limited status in February 2012 and became unlimited.
In its last set of accounts as a limited company, the business had tax profits of €1.17m for 2010 and €1.2m for 2009.
Queries submitted to Country Clean and Panda Waste about their reasons for adopting offshore ownership structures received no response.