Is it der, die or das Abmachung? – die Abmachung, plural die Abmachungen

Why is it die Abmachung?

Abmachung ends in -ung, and nouns ending in -ung are feminine: in a German dictionary, 99% of them take die.

Sense 1

die

[1] An oral or written agreement that is binding and effective

[1] eine mündliche oder schriftliche Vereinbarung, die bindend und wirksam ist

[1] Oral agreements are contractually legally effective
[1] Mündliche Abmachungen sind vertraglich rechtswirksam.

[1] According to the written agreement, I can hold a dog
[1] Laut schriftlicher Abmachung darf ich einen Hund halten.

More source examples (1)

These dictionary examples can include historical and less common uses.

[1] "This agreement liked Mirä"
[1] „Diese Abmachung gefiel mir.“