Ich würde es so formulieren:

There are currently 10 vacation days left for this year.

My remaining holiday (vacation) entitlement for this year / the current year amounts to ten days
oder, einfacher:
I have ten days' holiday left this year

I still have ten vacation days left (this year)

I'd say in AE.

dude's suggestion works very well in AE.

A bit "filled out," some options could include (based on the choice of words in parentheses):

I (still) have ten (unused) vacation days (left) (for) this year.

e.g. "I have ten unused vacation days left for this year."