Related Clues:

• Return addressee, briefly?
• E-File destination
• Org. whose roots go back to the Civil War
• 1040-issuing org
• Tax org
• With 3-Down, many a tax auditor
• Auditor's org
• Gp. with a complicated code
• Grp. with a complex code
• Its Web site has a ''Where's my refund?'' page
• Org. concerned with the word spelled by the starts of 18-, 24-, 36-, 54- and 59-Across
• Tax-collecting org
• See 16
• Big collection agcy
• Taxing org