De or het referendumcommissie?

The correct Dutch article is:

de referendumcommissie

Rule Words ending in -tie and -sie: almost always de. See the rule

How to use referendumcommissie

the referendumcommissiede referendumcommissie
this referendumcommissiedeze referendumcommissie
that referendumcommissiedie referendumcommissie
our referendumcommissieonze referendumcommissie
your referendumcommissiejouw referendumcommissie
every referendumcommissieelke referendumcommissie
which referendumcommissie?welke referendumcommissie?
a big referendumcommissie / the big referendumcommissieeen grote referendumcommissie, de grote referendumcommissie