If the figure "Amount to be refunded to you" on the Virginia state income tax form looks unusually high this year, don't go out and put a down payment on the Porsche. All is not as it appears.

About 25 per cent of Virginia's taxpayers are mistakenly giving themselves a tax break on their state income tax returns due to the disappearance of three words on the federal income tax short form, the familiar 1040A.

"We've been thrown for a loop," said Edward A. Dore, director of the state's income tax division. "I don't know what the ultimate answer is going to be."

The problem apparently arises from the Internal Revenue Service's decision to remove the words "adjusted gross income" from the federal income tax form used by those who do not itemize their deductions. In their place the word "Total" now appears.

Unfortunately for the Commonwealth, Virginia's state income tax short form asks the taxpayer to enter the figure for his adjusted gross income on the federal form as the starting point for computing his state income tax.

To reach the correct figure, Virginia taxpayers should use the line on the 1040A form that is now marked Total. Instead, according to Dore, many of them are entering the figure on the back of the short form marked "taxable income," since there is no longer a figure marked adjusted gross income to enter.

Taxable income, however, is the amount left after the taxpayer has subtracted the standard deduction and exemptions. When it is used as the starting figure on the Virginia form, Dore said, the taxpayer subtracts standard deductions and exemptions twice, leaving him with a smaller income to be taxed and, in many cases, a much larger refund.

About two-thirds of Virginia taxpayers receive refunds from the state, Dore said. By using the wrong figure from the federal form, those refunds are increased by as much as $140.

To correct the problem, Dore's staff is sifting through each return to see if an error has been made and is asking each local jurisdiction to do the same. In Arlington County, where about 10 per cent of the state forms have been returned, the error rate is running about 33 per cent, according to Joan Bender, assistant to the county commissioner of revenue for income taxes. Most of the income forms, Bender said, are simply corrected and sent on to Richmond. The others are returned to the taxpayer who is instructed to try again.

The problem is compounded, Dore said, by taxpayers who, in talking to their neighbors, have discovered that they have computed themselves less of a refund than their neighbors by filling out the forms which are filled out with the mistake included.

"It's a mess all right," Dore said.