With rising fuel prices and a slowing economy, these are tough times for Bilbo Transports Inc., a family-owned trucking company based in Irving.

Times are about to get tougher, company Vice President Mike George said, when a new state business tax comes due a month from today.

There is widespread confusion about the tax because no other state taxes businesses in the same way, and everything about it is new, including the vocabulary and forms. Final versions of the tax forms were not even available until the end of the March.

Some business owners say the tax is hitting them too hard.

Bilbo Transports paid as much as $12,000 a year for the state's previous franchise tax. Under the new margin tax approved by the Legislature in 2006, the company's tax bill will soar to an estimated $150,000 to $170,000 this year, George said. "It is crippling us."

He said the new tax burden might lead to layoffs of some of his 45 employees or other cost-cutting measures.

About 900,000 Texas businesses — including 200,000 that were not subject to the previous franchise tax — will pay the margin tax. It is the first major revision of the tax since 1991, when the original 1907 version was updated to reflect the modern economy and address a number of legal issues.

For most qualifying businesses, the tax is 1 percent of their gross revenue minus one of three options: the cost of goods sold, employee compensation or 30 percent of total revenue.

The state estimates that the new business tax will raise almost $12 billion in the next two years, more than double what the previous tax generated. But solid revenue numbers are not expected until August, the deadline for businesses that filed for an extension, said R.J. DeSilva, spokesman for the state comptroller's office.

The additional money coming to the state will go to school districts, which were required to reduce their property tax rates as part of the same legislative deal that spawned the margin tax.

Alan Sherman, a Dallas lawyer who writes a state and local tax blog, said his blog has been hopping in recent weeks with questions about the margin tax from both business owners and accountants.

"Suddenly there's a real practical personal interest," Sherman said.

Christi Mondrik, an Austin lawyer and accountant who has been conducting training on the new tax at seminars organized by professional associations, said many businesses have been surprised to see how much they actually owe.

Some of the biggest surprises are for businesses in the service industry that have high capital costs, such as planes, trucks and other equipment, Mondrik said.

The new tax hits trucking companies particularly hard because often most of their workers are independent contractors. That means much of the company's labor costs cannot be deducted from its taxable revenue.

At Bilbo, 90 percent of the company's drivers are independent contractors who own their trucks.

"We find that we get superior service from those guys because they are motivated as their own independent businessmen," George said.

So, the company's total revenue includes what it charges customers for the drivers as well as their trucks and fuel. The company is taxed on that full amount even though it does not profit from those pass-through items.

Some businesses will see a substantial tax increase under the new tax, said Dale Craymer, chief economist for the Texas Taxpayers and Research Association.

"But that may be more a function of how well the old tax code treated them or how well they took advantage of it," Craymer said.

Many taxpayers benefited from the lowering of property tax rates that was coupled with the new business tax. Bilbo's property tax bill fell $7,000 between 2006 and 2007 because of the mandatory rate decrease but not nearly enough to offset the company's obligation under the new margin tax, George said.

The change also shifted more of the tax burden to the service industry, which had been lightly taxed under the old system, Craymer said.

"But while businesses are taxed more equally under the new margin tax, the tax is still too big," Craymer said.

Kurt Summers, president of Austin Generator Service, agreed that the tax is too big.

The 15-employee company, which sells, rents and maintains power generators, paid $4,000 to $8,000 a year for the franchise tax and expects to see its payments double under the new margin tax, Summers said. His property taxes, in turn, dropped about $1,000 last year.

The company has a well-established market so it will be able to weather the change, Summers said, but he will think twice before adding employees or buying equipment because of the new expense.

Will Newton, executive director of the National Federation of Independent Business/Texas, said many small businesses are going to be walloped by the new tax because they often have low profit margins, higher overhead and tough competition.

Despite some provisions to ease the burden on small businesses with revenue under $900,000, for some of the businesses "it could just be enough to put them under and put them out," Newton said.

Taxes due; post offices open late

Today is the deadline to file federal income tax returns. Several post offices will have extended hours to accommodate last-minute filers. Returns must be postmarked by midnight.

The main Austin post office at 8225 Cross Park Drive will be open until midnight to accept tax returns. Services such as certified mail will be available through the automated postage center at that site.

Five other stations will have extended hours. Chimney Corners, 3575 Far West Blvd.; Mockingbird Station, 7310 Manchaca Road; and the Oak Hill Station, 6104 Old Fredericksburg Road, will be open until 7 p.m. The downtown post office at 510 Guadalupe St. and the station at 11900 Jollyville Road will be open until 6:30 p.m.

Margin tax basics

Who pays?

Any legal entity that does business in Texas and is organized to have some form of limited liability protection, including corporations, partnerships and business associations.

Who doesn't pay?

Sole proprietorships and general partnerships that have only individuals as partners. Entities with gross receipts of $300,000 or less.

What is the deadline?

May 15 (to pay or file for an extension).

For more information: www.window.state.tx.us/taxinfo/franchise