@shanesnh having gone through both your posts on this thread:
(a) To be able to use FEIE ( with a Foreign Tax home ) to mitigate the effects of double taxation { per your statement your US Tax burden is Zero ) you need to file a Federal Return. As a US Person ( Citizen/ GreenCard ) you are required by law to recognize your world income which you do by filing a tax return.
(b) You are also , as a US person under the FICA/SECA obligations . However, because South Korea and US have a Totalization agreement in effect, you need to pay FICA/SECA to only on e country . You do this by submitting a certificate of Participation ( from the country you participate in ) to the Non-Participating country. This also implies that your Govt. pension ( Social Security or its equivalent ) is paid by that country and taxed ( generally ) only b y that country.
( c) Unless your NRA Spouse wishes to expose her world income to US taxes ,
1. She does not need a TIN ( in her case ITIN ) and therefore no need to file by mail along with the W-7 application and the supporting documents.
2. You can only file as MFS (Married Fling Separate ) which will need you to file by mail -- because TurboTax ( and IRS ) requires details of the Non-Fling Spouse -- Name, TIN, etc. The only way to do this is to satisfy the software error checks by using a dummy TIN ( for the non-filer ) and then print and replace this with "NRA". That is why the need for filing by mail. Note that the IRS XML definition of the fields of the form 1040 expects a Numeric field for TIN. Therefore Tax software generally check for valid TIN ( and this would be disabled for allowing entry like NRA . When processing paper returns there is a curative process with human intervention.
(d) It would be interesting to confirm and understand how the other Tax Software ( you mentioned ) achieve allowing NRA in numeric field --- perhaps lowering the checks to allow a number like 000-00-0000 or similar reserved number stream, at the expense of entry error checking. Obviously it is possible
Hope this answers your query . Is there more I can do for you ?
pk
