You can't tell from the amount of tax that you owe. If the 1099-R is for an IRA distribution (the IRA/SEP/SIMPLE box is checked) the amount that is included in your taxable income is on Form 1040 line 4b. If the 1099-R is for a pension or annuity (the IRA/SEP/SIMPLE box is not checked) the amount that is included in your taxable income is on Form 1040 line 5b.