This is the 11709th most frequent Korean word.
납입
Payment or submission.
Here, "납입" refers to 'payment or remittance' and is used as a noun to indicate the act of paying or depositing something, typically money.
납입 기한이 다가옵니다.
The payment deadline is approaching.
In this usage, "납입" functions as a verb (by conjugation), meaning 'to pay or deposit money,' commonly associated with formal payments like tuition.
등록금을 납입해야 합니다.
You need to pay the tuition fee.
"납입" is used in combination with '증명서' (certificate), referring to a certificate proving payment or deposit has been made.