De or het billing?

The correct Dutch article is:

de billing

Rule Words ending in -ing: almost always de. See the rule
Meaning (Dutch) (boekhouding) het in rekening brengen van te betalen bedragen

How to use billing

the billingde billing
this billingdeze billing
that billingdie billing
our billingonze billing
your billingjouw billing
every billingelke billing
which billing?welke billing?
a big billing / the big billingeen grote billing, de grote billing

Meaning, plural, diminutive, pronunciation and translations: WikiWoordenboek (Dutch Wiktionary) (CC BY-SA 4.0). Example sentences: Tatoeba (CC BY 2.0 FR).