Guernsey could lose up to £80m if corporation tax is scrapped, according to an independent report.
The study was carried out by a panel consisting of a former States member, an economist and an independent economic consultancy group.
The report concluded the "zero-ten" tax model proposed by the Policy Council was the only viable option.
A "zero-ten" system means some companies would pay 0% tax, while others would be taxed at 10%.
The panel, which ruled out a "zero-twenty" alternative as "too risky", said retaining the finance industry in the island was vital.
The Isle of Man announced in its budget in February that it would introduce the "zero-ten" system.
It is one of Guernsey's main rivals in the finance industry and Jersey has also decided to adopt a similar arrangement.
The independent report has also estimated the States could suffer a loss of income between £50m and £80m, depending on what measures were introduced, and how islanders responded to them.
The island's government has been preparing for a predicted £48m budget deficit when corporation tax is abolished in 2008.