I am employed full time and am in the process of starting a t shirt business on the side (sole proprietorship), while still keeping my current position. When filing at the end of the year do I have to pay SS and Medicare tax if that is already being paid for me by my full time employer?

Also, will I be filing a separate income tax filing or will it be incorporated into my standard filing. Thank you!

Yes, you pay SS on ALL income.

You would file (depending on how your business is being formed) with additional schedules (to put it simply) but on one income tax return.

You do not seem familiar with legal situations and I would respectfully suggest that you run your business plan past an Attorney. You can get yourself into problems with both State and Federal authorities.

My brother in law is an attorney and said I should speak to an accountant which is why I was posting here. I was looking for a response from an accountant. I am just trying to glean some information prior to paying for said service.

Please don't attempt to direct who will answer your questions. I'm surprised that your brother in law, the attorney, didn't realize you have to pay SS on all income.

You obviously need PAID advice from an attorney and an accountant.