De or het contractonderhandeling?

The correct Dutch article is:

de contractonderhandeling

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

How to use contractonderhandeling

the contractonderhandelingde contractonderhandeling
this contractonderhandelingdeze contractonderhandeling
that contractonderhandelingdie contractonderhandeling
our contractonderhandelingonze contractonderhandeling
your contractonderhandelingjouw contractonderhandeling
every contractonderhandelingelke contractonderhandeling
which contractonderhandeling?welke contractonderhandeling?
a big contractonderhandeling / the big contractonderhandelingeen grote contractonderhandeling, de grote contractonderhandeling