My spouse and I have simple taxes, but when we prepare them as MFJ we end up owing money. When we prepare them MFS, we both get a refund. Why?

[Anonymous]

What are we doing wrong? I thought MFJ is beneficial in most cases. Our taxes are very straightforward. We both had one job the whole year, we didn't move, we don't have a house, both taking standard deduction. We make about the same amount of money, he makes slightly more. However, when we file jointly we ended up owing money and when we filed separately, we both got a refund.

[Anita01]

You cannot do a joint return then change the marital status to separate and get any kind of a reasonable answer.  You also cannot change the return back to joint and have a correct return.  You would need to prepare a joint return, then two separate ones by starting each one over.

[Anonymous]

That answer does not help. We did mock returns to see which way we should file. MFJ or MFS.  I am wondering why there is such a discrepancy....