Even if its almost a year since I am back from USA this period of life is not yet checkmarked completely. Everyone who earns a Penny is obliged to file a (federal) tax return. This must be done until April, 15th of the following year. So did I.To file the federal tax return I had some help from CDS, the organisation which helped obtaining the US visa. They provided a web-based application to create the tax return step by step with helpful explanations and hints. As only permanent residents of the US are allowed to file the tax return electronically, I was obliged the print and mail the return. Filing the Georgia state income tax was up to me as in my case there is no law which says I have to file a return. But as there was any potential windfall in prospect I had to do this return as well, of course. 
Finally, it was not as difficult as I expected. After reading all the corresponding forms and remarks on the sheets it can be done easily. So I sent both tax returns still in time to the United States of America.The federal refund reached my US bank account in April, only a couple of weeks after sending all papers to the IRS.The Georgia state tax return took al little longer. At least the Georgia Department of Revenue lets you follow up the 
estimated refund date on their website. But when my refund was due and did not arrive in any way I contacted them directly and got an astonishing answer: Their worked through my papers but the did not send any check because I am no resident. But now, they explained, a check will be mailed to my German address. And so did they. Almost after one year I got my last “paycheck”. Finally, I did not pay any tax at all! 