Hey guys,
I also had issues with the Coding for S/D and did some research. According to IRS: "Code S—Employee salary reduction contributions under a section 408(p) SIMPLE plan. Show deferrals under a section 408(p) salary reduction SIMPLE retirement account. However, if the SIMPLE plan is part of a section 401(k) arrangement, use code D. If you are reporting prior year contributions under USERRA, see the TIP above Code D under Box 12—Codes."
Therefore use Code D instead of Code S, even though it is a Simple IRA, our employers does have it as 401k arrangement. They are coding it wrong and I don't know why Code S won't work but I changed it to Code D and it went through. Good luck!
