The Internal Revenue Service opened the 2005 tax filing season Monday with expanded electronic services and eased tax filing rules.

The filing deadline is April 15.

The IRS estimates that 133 million individual taxpayers will file returns, with 50 percent or more doing so electronically for the first time. Last year, nearly 62 million Americans used e-file.

The IRS expects to process more than 617,000 individual Maine tax returns.

The IRS is taking steps in several areas to help taxpayers. Many of these features can be found on IRS.gov, including:

• Added help for the Earned Income Tax Credit, or EITC. The EITC Assistant, available in English and Spanish, will allow taxpayers to type in a little information and follow directions to determine if they are eligible for the credit.

• Expanded 1040 Central. Taxpayers again will find a one-stop resource for tax return information by visiting 1040 Central on IRS.gov. The newly expanded page will connect taxpayers to basic income tax preparation needs such as key forms, answers to frequently asked questions and links to information on key tax issues.

• “Where’s My Refund?” The popular “Where’s My Refund?” function on IRS.gov allows taxpayers to get the answer to the most frequent question they pose during the tax year. Taxpayers may find refund information by submitting their Social Security number, filing status and the exact amount of their anticipated refund. Last year, it was used 20 million times.

• Simpler forms for more taxpayers. The income limits for using the Form 1040EZ and Form 1040A will increase from less than $50,000 to less than $100,000. Last year, about 18 million taxpayers filed a Form 1040EZ and another 24 million filed a Form 1040A. The change means 1.6 million more taxpayers are eligible to file the 1040EZ or 1040A.

The one-page Form 1040EZ is for taxpayers who have no dependents, no credits other than the Earned Income Tax Credit and no adjustments to their income. The Form 1040A is for taxpayers who do not itemize their deductions, claim limited tax credits and have few adjustments to their income.

• Simpler forms for the self-employed. The limit on business expenses for self-employed individuals using Schedule C-EZ also will increase to $5,000 from $2,500. This change will mean 500,000 more small business owners and self-employed taxpayers can use the simpler version of the expense form.

In addition, there are recent tax law changes that affect tax returns filed in 2005 for the 2004 tax year.

One of the biggest involves the new sales tax deduction. Taxpayers who itemize deductions will have a choice of claiming a state and local tax deduction for either sales or income taxes on their 2004 and 2005 returns.

Other tax law changes affect such areas as charitable donations, child tax credit and combat pay issues.