@SteamTrain, @AmyC
Thank you both. We found the issue.
It turns out that my wife falsely filled out a tax exemption code "E" there to request all tax paid to MA before her work location was really adjusted from CT to MA since May last year. The problem is, she doesn't qualify for being exempt from CT tax because her income is from CT before May, which exceeds $24,000 (married joint filing) as required by CT to be tax exempt. That's why we can see some CT wages shown on W2 (nearly half of her whole year income), but we don't see any CT tax withheld because the code "E" she put there instructed her company not to do so! She paid all tax to MA throughout the year!
Now my question becomes, can I apply the portion of tax she paid to MA (our resident state) as a credit to CT (non-resident) tax liability? I notice the instructions in CT Schedule 2 form describes such a case. The amount of credit we can apply looks like below.
CT source income
------------------------------------- x (tax paid to MA)
Her total income for 2021
Does this look right?
