noun
balance due; arrears
Refers to an amount of money that remains unpaid after the due date; used in billing, accounting, and debt contexts.
先月の払い残りがまだあるので、早めに支払ってください。
There is still a balance due from last month, so please pay it promptly.
払い残りが溜まると督促状が届く。
If arrears pile up, you'll receive a reminder notice.
Compound of 払い (payment) + 残り (remainder). The exact historical derivation is uncertain, but the meaning is transparent from its components.