PROVIDENCE — Estimating that taxpayers already are kicking in an average of 12.3 percent of their income to finance state and local government, the Rhode Island Public Expenditure Council urges that Governor Carcieri and the legislature be wary of making any sudden changes in the tax structure as a quick fix for the looming budget crisis.

“Before any changes to the tax structure are made, they ought to be analyzed in a fair amount of detail,” said John C. Simmons, executive director of the business-backed organization that studies public fiscal matters.

“We’re saying you have to do this in a thoughtful way,” especially, he said, because the legislature has made changes to the tax code in recent years and it will take some time to gauge their effects.

One change is the flat tax option passed by the General Assembly in 2006. Another reduced the capital gains tax on assets held more than five years.

“Those changes are just starting to hit,” Simmons said.

“You should know what the impact is in the long term,” said Susanne Greschner, policy director for RIPEC.

She said the organization may, over the next month or so, offer some further proposals for changing the way people and businesses are taxed. It will also be looking at how the state is spending its money.

“Sometime in April we’ll have some recommendations on what should be done,” Simmons said.

Rhode Island’s tax burden is the seventh-highest in the U.S., according to a RIPEC study released last week that ranked Connecticut 11th and Massachusetts 34th. According to the RIPEC analysis, Rhode Islanders pay less personal income tax than those states but pay more in general sales and use taxes.

Just over 42 percent of the Rhode Island taxes expected to be collected in the next fiscal year will come from the personal income tax; the ratios are 60.7 percent in Massachusetts and 60.2 percent in Connecticut.

General business taxes, on the other hand, are expected to contribute 15.2 percent of the revenue in Rhode Island versus 10.6 percent in the Bay State and 9.7 percent in Connecticut.

General sales and use taxes are also projected to be much higher in Rhode Island than neighboring states according to the report, available at www.RIPEC.org. They will make up 34.1 percent of the taxes collected here, versus 14.8 percent in Massachusetts and 28.3 percent in Connecticut.

The report says Rhode Islanders have seen the total amount of taxes collected from them from 1995 to 2005, the latest year for which complete numbers are available, increase by 4.6 percent, even as collections per $1,000 of personal income have remained stable or declined in Massachusetts, Connecticut and the U.S. as a whole.

The amounts dropped by 5 percent in Massachusetts, 2.8 percent in Connecticut and 0.3 percent in the U.S.

But the type of tax people have been paying has differed from state to state.

Income taxes increased 15.2 percent in Rhode Island but dropped 3 percent in the Bay State, rose 26.3 percent in Connecticut and rose 4.9 percent throughout the country.

Sales tax collections rose 13.1 percent here, but dropped in the other two states — down 6.2 percent in Massachusetts and a hefty 14.3 percent in Connecticut. They dropped 1.4 percent in the U.S.

gemery@projo.com