De or het loonheffingskorting?

The correct Dutch article is:

de loonheffingskorting

Rule Words ending in -ing: almost always de. See the rule

How to use loonheffingskorting

the loonheffingskortingde loonheffingskorting
this loonheffingskortingdeze loonheffingskorting
that loonheffingskortingdie loonheffingskorting
our loonheffingskortingonze loonheffingskorting
your loonheffingskortingjouw loonheffingskorting
every loonheffingskortingelke loonheffingskorting
which loonheffingskorting?welke loonheffingskorting?
a big loonheffingskorting / the big loonheffingskortingeen grote loonheffingskorting, de grote loonheffingskorting