While it's generally the case that a married person can't be claimed as a dependent on someone else's return if the married person files a joint return, an exception applies.
According to the Exception under Joint Return Test in IRS Publication 501, Dependents, Standard Deduction, and Filing Information, "You can claim a person as a dependent who files a joint return if that person and that person’s spouse file the joint return only to claim a refund of income tax withheld or estimated tax paid."
This reflects the text in the What needs to be done description.
If you want to file as Married Filing Separately, you can claim the personal exemption for your spouse only if they:
- Had no gross income, and
- Aren't filing a return, and
- Weren't the dependent of another taxpayer.
