Arlington police have begun a criminal investigation into whether the county treasurer's office improperly altered a taxpayer's check transforming a $26.22 check into one for $262.20.

The investigation has focused attention on what Arlington Treasurer Bennie L. Fletcher defended yesterday as a "long-standing procedure" of correcting "seeming ambiguities" in any checks to match tax bills.

Fletcher, a 56-year-old Republican currently seeking reelection, acknowledged, however, that the $26 check that has prompted the police inquiry "looks as if" it had been altered in violation of his own rules.

Fletcher said his office may make as many as 50 corrections a year to checks, inserting the proper value which a special rubber stamp that carries his name.

Although Fletcher said the practice is really designed to benefit taxpayers, saving them any penalties for late payments, state officials said yesterday the treasurer's office has no authority to change the value of any check.

"I know of no statutory authority permitting a treasurer to change the amount of a check," said Ken Thorson, an attorney in the State Department of Taxation in Richmond.

Fairfax County Treasurer Warren Hutchison said that "less than 10 times per year" his staff corrects the amount on checks if numerals and writing on the check differ. "But we oly fool around with a few cents, never anything in the dollar range," Hutchison said.

Alexandria Treasurer Elizabeth Bell said her office returns all incorrect checks -- including those with incorrect dates -- to taxpayers.

That is what Robert Troutman, a 22-year-old Arlington school bus driver whose wife Karen wrote the $26 check, says he wished Fletcher's office had done. "We were absolutely furious," he said, when his bank told him his checking accoung was overdrawn because of the $262.20 check.

'It's a very strange case," said police Captain Lendel Holsclaw, who said that a variety of laboratory tests will be performed on the Troutman check his week. "We don't know who changed the check. If somebody put money in their pocket, then we'd have to start looking for who did that, but I don't know if helping Arlington County collect their taxes is against the law."

Arlington prosecutor William S. Burroughs Jr. refused to comment on the investigation yesterday. But Fairfax deputy commonwealth's attorney Steven A. Merril said that it was unlikely that whoever changed the check could be subject to charges of forgery and grand larceny unless prosecutors could show the worker actual with criminal intent.

"It's a heck of a move by somebody," Merril said. "If there was a crime for stupidity, well, whoever did this would certainly be guilty."

Karen Troutman, the 21-year-old government secretary who wrote the check said she was unaware she had underpaid the taxes on her 1978 MGB automobile until she received a notice from First Virginia Bank saying that the family's checking account was overdrawn.

"We couldn't figure it out," said Robert Troutman "so we went through our canceled checks and found out that the numbers on the check Karen wrote had been changed in different colored ink and the correct amount ($262.20) was filled in."

Troutman said he was so angry "I called Mr. Fletcher at home and he told us it was common practice to change checks like that."

Troutman's efforts to swear out a criminal warrant against Fletcher were also frustrated. Troutman said an Arlington magistrate told him "that he [Fletcher] is an elected official and he's running for reelection" and refused to issue a warrant.

Dickson Foster, assistant manager of First Virginia's Shirlington branch, said that although it was "obvious that someone changed the amount" on the check the bank processed the check anyway.

"Things like that happen," Foster said. "Maybe it was a busy day. If it's altered, it's not the bank's fault. It's the fault of whoever altered it. I told him [Troutman] to straighten it with the treasurer."

Flether said that he believes the Troutman check was altered before it reached his office even though it bears a stamp from his office carrying the higher value.

"If we sent the checks back," Fletcher said, "then the taxpayer would have to pay a 10 percent late fee for missing a tax deadline. Besides, if we notified everybody that their check was wrong, we'd never get anything done." CAPTION: Picture 1, Bennie L. Fletcher . . . "long-standing procedure;" Picture 2, Robert and Karen Troutman of Arlington display check for taxes that has been altered from $26 to $262.20. By Ellsworth Davis -- The Washington Post; Picture 3, This is the check Robert andd Karen Troutman sent to the Arlington Treasurer's office. By Ellsworth Davis -- The Washington Post