I’m going to lose five kilos by the end of this month.
This company exploits its employees too much, so I'm bailing out at the end of the month!
My boss pays me in koala bears. I get two at the end of every month.
You know how 月 can also mean month? If you add 末 on there you have the "month end" aka the end of the month.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.