Right now I put about 96% of my paycheck into my SIMPLE IRA so the other 4% covers my share of the taxes. I make less than $11,500/year so I can do that. If I can pay my taxes at year end then I will put 100% into my IRA instead. Can I or do they have to paid when my employer pays its share?

Even if you are self employed you have to pay quarterly (then you wouldn't HAVE an employer)... nobody gets to wait until the end of the year to get current.

How is your employer NOT withholding your share of taxes? They are required to unless you are a 1099 contractor and then YOU have to pay EVERYTHING quarterly (because you are your own employer).

My employer IS withholding my share. I don't want to be sending checks to the gov't every other week which is why I leave about 4% every paycheck in there to cover my taxes (net is $0 paycheck). Of course I'm paying withholding on the 4%...

Kimski:

4% is NOT enough to cover your FICA (Social Security @ 4.2% and Medicare @ 1.45%) tax obligations, as they are FLAT taxes withheld at the percentages noted.

I suspect that, for some reason, you are being treated as a 1099 contractor or perhaps a statutory employee and NO FICA taxes are being withheld.

The 4% is "about" and varies. It gets adjusted so that my paycheck is $0. I am an employee that gets a W-2. I'd like to put 100% in my IRA. If I do, when do I have to pay my FICA taxes-monthly, quarterly?

YOU cannot pay FICA taxes; it MUST be paid by the employer.

Both the employer AND employee pay FICA taxes.

As I reread your comment I think you mean that the employer is the one who actually sends the money to the gov't. I'm going to check with our accountant and she what she says.

What ATE is saying is that it is the responsibility of the employer to make payments of FICA taxes. They pay the employer portion AND forward the withheld employee portion.

If you believe you are underwithheld for the year, you can make quarterly estimated payments. But these payments are not specifically FICA but are a general payment that is used to reduce any payment due once your actual tax liability is determined.