De or het inlegering?

The correct Dutch article is:

de inlegering

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

How to use inlegering

the inlegeringde inlegering
this inlegeringdeze inlegering
that inlegeringdie inlegering
our inlegeringonze inlegering
your inlegeringjouw inlegering
every inlegeringelke inlegering
which inlegering?welke inlegering?
a big inlegering / the big inlegeringeen grote inlegering, de grote inlegering

Dutch words ending in inlegering

tinlegering

In compound words, the last part decides the article. See the rule