月底

yuè dǐ jié suàn

月底结算

settle accounts at the end of the month

yuè dǐ yǐ qián

月底以前

before the end of the month

qǐng zài yuè dǐ qián quán é fù qīng

请在月底前全额付清。

Please pay the full amount (=of money) by the end of the month.

bǎ jié zhǐ rì qī yán zhì yuè dǐ

把截止日期延至月底

extend the deadline until the end of the month

tā men zài yuè dǐ jǔ xíng yī gè cí shàn wǔ huì

他们在月底举行一个慈善舞会。

They're holding a charity ball at the end of the month.