Not always. The IRS has information that has been provided by to them by third parties reported on various forms 1099 or 1098 from banks, customers &, educational institutions among others.
There may be other taxable income and deductions the IRS has no record of that should be used as well when preparing your taxes. Some examples are state withholding taxes which appear on form W-2, the taxable income you may have received from self-employment that the payee has not reported on form 1099 and of course they have no idea of what your business deductions are either.