End-of-year congressional votes to change the tax code have created havoc for the Internal Revenue Service and top the list of problems bedeviling taxpayers, according to an annual report released Wednesday.

The National Taxpayer Advocate also accused the IRS of not doing enough to help the insolvent -- including those losing their homes -- avoid paying taxes on canceled debts and not providing fee waivers to low income taxpayers.

Taxpayer Advocate Nina E. Olson urged Congress to enact a Taxpayer Bill of Rights and to authorize symbolic apology payments to those seriously affected by IRS errors.

The National Taxpayer Advocate, who works independently within the IRS, is required by Congress to report annually on at least 20 of the most serious problems facing taxpayers.

A year ago, the advocate focused on the alternative minimum tax, the levy originally aimed at ensuring that a small number of the superrich pay taxes. Because it was never adjusted for inflation, the tax now affects millions of upper-middle income level people.

This year the main culprit was Congress, which for the second straight year passed legislation in December that significantly changed the tax code.

The problem? The legislation was enacted after the IRS normally goes to print with forms for the coming tax season.

In 2006, Congress waited to extend several popular tax deductions, and the advocate said taxpayers made an estimated 1.4 million fewer claims for those benefits in 2006 than the previous year because information on the benefits was not included in the original forms.

Some low-income people who claim the earned income tax credit, a refund averaging more than $3,000, had to wait weeks for that refund while the IRS reprogramed its computers. For some, Olson said, that delay could mean eviction, the inability to pay winter heating bills or defaulting on credit card bills.

Last month Congress finally took steps to shield more than 20 million from getting hit by the alternative minimum tax. The IRS has said that more than 13 million taxpayers may have to wait until Feb. 11 to file their returns while the agency updates its programs to reflect the changes.

Congress recently took steps to protect people losing their homes from taxes levied on canceled debts, but the report said the IRS does not adequately explain exceptions to the general rule that such canceled debts are taxable.

The IRS also collects about $180 million a year in user fees, mostly charges to people who enter into installment agreements to pay tax liabilities over time. But here too the agency lacks an adequate policy for waiving fees for low-income taxpayers who can't afford the fees, the report said.

The report also takes up a perennial problem, the estimated $290 billion gap between what taxpayers owe every year and what the IRS collects. It said that unreported income from the cash economy is probably the single largest component of the tax gap, and urged the IRS to create a cash economy program office to coordinate efforts to address the issue.

The private debt collection program, under which the IRS farms out smaller scale delinquency programs to private collection agencies, also got repeat mention. Olson repeated her position that the program be eliminated, saying that so far the costs of the program have exceeded the revenue generated. The goal of the program had been to raise between $1.5 billion and $2.2 billion over the next 10 years.

Among other problems:

--Tax preparers continue to sell products such as refund anticipation loans under which lower income people at times get hit by high interest rates in exchange for getting advances on expected refunds. The IRS says it is proposing steps to restrict such practices.

--IRS identity theft procedures, while better than they were in the past, too often apply more scrutiny to the victim of identity theft than the perpetrator.

--Taxpayers who visit IRS taxpayer assistance centers continue to have difficulties making appointments, obtaining return preparation assistance and making payments.

A National Taxpayer Advocate study found that low-income taxpayers do much better in EITC audits when they are represented by practitioners, suggesting the examination process is flawed.