Enter the regular elective deferral (up to $18,000) and the catch-up elective deferral (up to $6,000) in the separate boxes provided.

If you have contributed all of your net earnings as elective deferrals and employer contributions to your 401(k), you have nothing left to contribute to an IRA.  The sum of the amounts on Form 1040 lines 27, 28 and 29 cannot exceed your net profit from self employment.  Also, the sum of the amounts on Form 1040 line 27, Form 1040 line 28 and your IRA contributions cannot exceed net profit from self-employment.