What does COOPT stand for on a car registration fee?

[danehernberger · Accepted solution]

It means County Option tax, which in most cases is the only deductible part of registration fees.

[rachelrene12]

Would this be the same thing as just "county tax"? That is all that shows up on my vehicle registration statement.

[jllcmsprl]

Yes. Per the Montana DMV website, COOPT is the same as County Tax

[Always-Seeking-Knowledge]

COOPT is indeed the only deductible part on Federal, despite the TT instructions.  LVREG is not deductible on Federal because it's based on model year (age).  See the help item right there.  LVREG is deductible on Montana itemized deductions.