For tax years 2018 and after - Personal exemptions are no longer included on the tax return. By filing a joint return, your spouse is listed as a joint taxpayer and the return filed is for both spouses. If you file Separate returns, the spouse will need to file their own return (if required to do so).
For tax years prior to 2018 - If you are filing a Married Filing Joint return, the spouse is already included on the return. Do not enter the spouse as a dependent on the return.
If you are filing a Married Filing Separate return, you can claim the spouse's exemption if
- they had no gross income
- the spouse is not filing a joint return
- the spouse is not a dependent of another taxpayer.