WASHINGTON — Getting people to pay the taxes they owe could be one significant way of coping with dizzying increases in the federal deficit and the potential $700 billion pricetag for the just-enacted financial rescue plan, tax experts said Thursday.

In 2001, the last year the Internal Revenue Service estimated the tax gap — the difference between what taxpayers owe and what they actually pay — the figure stood at $345 billion, or $290 billion after subtracting enforcement efforts and late payments. The overall compliance rate for paying taxes was about 86 percent.

The tax exports, at a forum hosted by Sen. Tom Carper, D-Del., said that in spite of some IRS successes in improving tax compliance, the gap may have grown since 2001.

"We believe $345 billion is a low-ball estimate," said J. Russell George, Treasury Inspector General for Tax Administration.

By comparison, the federal deficit for the just-ended budget year was a record $438 billion.

Carper said he had told Democratic presidential nominee Sen. Barack Obama, D-Ill., that reducing the tax gap was "a good place to go" when considering how to pay for the financial rescue package. "There's some low-hanging fruit here," said Carper, who chairs the Senate subcommittee on federal financial management.

The IRS, in a 2006 study on the gap, concluded that $197 billion came from underreporting on individual income tax returns while $88 billion was from underreporting by corporations and the self-employed. The remainder came from those not filing.

George said more third-party reporting would boost revenues coming into the IRS. He said people subject to withholding from their employers report 99 percent of their income, while the self-employed report only about 68 percent of income. That figure drops to 19 percent for those self-employed paid on a cash basis.

Small businesses should be encouraged to participate in an electronic federal tax payment system which allows for scheduled, automatic payments, National Taxpayer Advocate Nina Olson said.