De or het pensioenplanning?

The correct Dutch article is:

de pensioenplanning

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

How to use pensioenplanning

the pensioenplanningde pensioenplanning
this pensioenplanningdeze pensioenplanning
that pensioenplanningdie pensioenplanning
our pensioenplanningonze pensioenplanning
your pensioenplanningjouw pensioenplanning
every pensioenplanningelke pensioenplanning
which pensioenplanning?welke pensioenplanning?
a big pensioenplanning / the big pensioenplanningeen grote pensioenplanning, de grote pensioenplanning