De or het loonvordering?

The correct Dutch article is:

de loonvordering

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

How to use loonvordering

the loonvorderingde loonvordering
this loonvorderingdeze loonvordering
that loonvorderingdie loonvordering
our loonvorderingonze loonvordering
your loonvorderingjouw loonvordering
every loonvorderingelke loonvordering
which loonvordering?welke loonvordering?
a big loonvordering / the big loonvorderingeen grote loonvordering, de grote loonvordering