The IRS 2013 tax table is available from IRS.gov. To access the table, use the Forms and Publications heading on the site's main page and then select the tab for Prior Year.
Tax tables are listed in the instructions that accompany each tax form on IRS.gov. The instructions for each form are listed to the right of the form. For the year 2013, the tax table for Form 1040 is on page 74 of the instruction booklet. The IRS website maintains forms, publications and instructions for prior years dating back to the late 19th century, but only the most recent four years are listed on the prior year forms and publications page. To search for forms and publications from earlier years, select the option to find all prior year forms and publications. This takes the user to a database searchable by the desired year.