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The accounting firm Pricewaterhouse Coopers filed Mitt Romney's taxes incorrectly two years in a row by listing him as a Utah resident, but Romney shouldn't be blamed for their mistakes, his attorneys argued in legal documents filed on Monday.

Romney, the Republican gubernatorial candidate, gave only his financial information and the amount of time he spent in Utah overseeing the Salt Lake Olympics, which his tax advisers then used to file his taxes in 1999 and 2000, his attorneys said.

"PwC's preparation of a part-year/nonresident tax return on (Romney's) behalf was simply incorrect, and that error was corrected when it was discovered," Romney's lawyers argued in a brief to the state Ballot Law Commission.

Romney's Pricewaterhouse Coopers advisers filed his Massachusetts income taxes as a part-year resident in 1999 and a nonresident in 2000. He amended both year's forms to Massachusetts resident in April, after deciding to run for governor.

The question of Romney's tax-filing status in those two years is central to the state Democratic Party's attempt to disqualify him from the ballot.

Democrats say Romney's tax filings prove he moved his legal residence to Utah, making him ineligible to run for governor under Massachusetts' seven-year residency requirement.

Romney, who with his wife has kept a home in Belmont for 30 years, says tax status does not determine legal residency.

Both sides on Monday submitted legal briefs summarizing their arguments to the state Ballot Law Commission, which plans to decide the case by Friday. It is believed to be the first time a Massachusetts candidate for governor has been challenged on the residency requirement.

Attorneys for the state Democratic Party said Pricewaterhouse Coopers accountants, who are experts in tax law and had been filing Romney's taxes for 20 years, did not make a "mistake," as Romney claimed.

Instead, the Democrats' attorneys said Pricewaterhouse Coopers made exactly the right determination in listing Romney as a part-year Utah resident in 1999 and a full-year Utah resident in 2000 -- and that Romney's decision not to call them as witnesses before the Ballot Law Commission last week proved it.

"They would have testified that they chose the correct returns in the first place because Mitt Romney was domiciled in Utah and not in Massachusetts," wrote the Democrats' attorneys, Joseph Steinfield and John Gilmore. "The so-called 'amended' returns were the mistake."

Romney said he realized Pricewaterhouse Cooper's error only late in 2001. It was then, his lawyers said, that he learned that since he was permanently "domiciled" in Massachusetts even while a Utah resident for most of 1999 and 2000, he should have filed Massachusetts resident taxes in those years.

Romney said when those taxes were originally filed, he was working nearly nonstop on the Olympics and relying heavily on his accountants. He said he signed his name next to bright yellow signs left by his accountants and dropped the forms in the mail without reading them.

A Pricewaterhouse Coopers spokeswoman did not return a call on Monday. Last week, a spokesman said the company would not comment on a case involving a client.

Romney's attorneys, John Montgomery and Peter Ebb, said the Democrats themselves could have called Pricewaterhouse Coopers as witnesses, especially since they are the ones who filed the challenge.

Montgomery and Ebb said Massachusetts has a tradition of leaders -- from Levi Lincoln in 1809 to William Weld in 1991 -- who did public service out-of-state in the years before they were elected governor.