Tax optimisation is no longer a matter just for the multinationals. A number of market players are now tailoring strategies originally drawn up for the corporate whales to the minnows, or small businesses and independent entrepreneurs. Whether the businesses are active in imports and exports, or in services, recent scandals involving document leaks, such as the so-called "Paradise Papers" earlier this month, show that a wider variety of companies are trying to lower their tax bills.

"When people talk about tax evasion, they think about multinationals. But the problem affects smaller companies, too," said Oxfam France spokeswoman Manon Aubry, noting that owners of several small and medium-sized firms have also been caught up in scandals recently. While tax evasion is illegal, there are a number of strategies that experts have devised for firms to structure their business operations to avoid tax. Called tax planning, tax avoidance, or tax optimisation, these strategies stay within the letter of the law, if not the spirit. Nevertheless, they are spreading.

"These are practices that are going mainstream," said Christian Chavagneux, an editorialist at the French magazine, Economic Alternatives, who has written a book on tax havens.

He dubbed it "the democratisation of fiscal optimisation," noting that the majority of the firms caught up in the Luxleaks scandal in 2014 were medium-sized. Nevertheless, given the opacity of the practice, it can be difficult to measure exactly how widespread it has become.

Jean-Eudes du Mesnil du Buisson, head of the French confederation of small and medium-sized businesses, CPME, said there was "no doubt some small and medium-sized businesses involved, but it is far from being a common practice."

By contrast, Paul Duvaux, a Paris-based tax lawyer, said he has seen "frequent use" of these tax schemes by owners of small businesses.

"Multinationals don't have anything on small businesses," he said. "These are legal practices. They only have to use the tools available to them."

Manon Aubry of Oxfam France said that, in reality, the use of such schemes was somewhere between commonplace and niche.

"For multinationals, what is at stake financially is much greater. But the cost of access to these schemes is sufficiently low to make them interesting to small and medium-sized businesses, as well," she said.