My question is about when does a self-employed tax payer have to make quarterly tax payments.
I understand that there is a safe harbor rule that says if you owed less than $1000 in taxes then you do not have to make quarterly payments in the current year even if your income is going to be much higher. Does the $1000 in this rule refer to income tax (only) or does it include Social Security / Medicare tax that you must pay. I believe to take advantage of this safe harbor rule, your total tax (income tax + your self employment tax) must be under $1000. Am I right about that?