Only in the simplest of cases. Yes, an employee with only W-2 income, some stock trades, some interest&#x2F;dividends.<p>But the IRS has no data feed to tell them what I did for rental property (schedule E), my side business (schedule C), my charitable deductions (schedule A), nor other schedule A items, nor gift tax return information, nor many other cases that arise from tax law complexity.<p>You could possibly calculate my &quot;most-pessimal&quot; tax liability automatically.