You can file all returns that are required (2013 will expire for any refund from Georgia on April 15th). I would do 2013, 2014, 2015 and 2016 for South Carolina as a nonresident and then amend the Georgia returns to receive a credit for taxes paid to another state on the same income.and if necessary amend 2016.
The federal return doesn't need to be amended but if you use TurboTax to do the amendments you change only the state returns. TurboTax will ask you if you want to amend the state return for any return you already prepared with our software. If you find that you need to prepare any return by paper you can select your state below to get the forms necessary to amend.
You will add a state return for South Carolina and file an original return for all years. Amend only Georgia returns after you have the nonresident returns done first. All returns will have to be mailed because e-file is not an option for a prior year.
Resident State: All income worldwide is required to be reported on your resident state return. Any money that is also taxed in a nonresident state allows you to use "credit for taxes paid to another state" when you complete your resident state return. Your resident state does not want you to pay tax twice on the same income. The credit will be the amount of tax charged by the nonresident state or the tax that would have been charged by the resident state, whichever is less.
Nonresident State: Any money earned in a nonresident state is required to be reported on that state tax return (with the exception of reciprocal agreements which does not apply in this case). The nonresident state will tax any income earned that is derived from that state or while you were in that state for work.How do I contact my state Department of Revenue? - TurboTax Support