If you are self-employed and contributing to a SEP IRA, SIMPLE IRA, or solo 401(k), you may be deducting your retirement contributions in the wrong place on your tax return without even knowing it. This common mistake doesn't just misplace a number; it can distort your self-employment tax calculation, throw off your allowable contribution amount, and cost you money. Read on to learn where the deduction actually belongs, why the distinction matters more than most people realize, and how choosing the right plan could potentially double your tax-sheltered savings.