Many businesses will be able to file their 2012 federal income tax returns starting Monday, Feb. 4. Filers of forms affected by January tax law changes will need to wait until late February or early March.

The Monday opening covers non-1040 series business returns for calendar year 2012, including  Form 1120  filed by corporations, Form 1120S filed by S corporations, Form 1065  filed by partnerships, Form 990 filed by exempt organizations and most users ofForm 720 , Quarterly Excise Tax Return. This includes both electronic filers and paper filers.

While many businesses will be able to file starting Feb. 4, there are a number of business forms still being updated for 2012. The IRS will announce soon when individual and business taxpayers can begin filing returns that include any of the delayed forms. Processing of these forms were delayed while the IRS completes programming and testing of its processing systems to reflect changes made by the American Taxpayer Relief Act (ATRA) enacted by Congress on Jan. 2.

A full list of the affected forms is available on IRS.gov.

In addition to the forms listed on IRS.gov, filing of two other business forms is affected by the delay, but only for electronic filers. Businesses using Form 720 and filling out lines 13 and 14 cannot file yet electronically, but they can file on paper. Other Forms 720 are being accepted electronically. In addition, Form 8849 Schedule 3, Claim for Refund of Excise Taxes, is not currently being accepted electronically, but it can be filed on paper.

Additional information will be posted soon on IRS.gov.