You can no longer use the "Married Filing Separately on the same form" filing status on your 2024 Montana return. Due to Montana's Income Tax Simplification bill that went into effect in 2024, you must now use the same filing status on your Montana return that you use on your federal return.
This means if you file as "Married Filing Jointly" or "Married Filing Separately" on your federal return, you'll need to use that same status for your Montana tax return. If you file separately on your federal return, you'll have to file two separate state returns as well.