1.
unpaid; overdue; non-payment
The state of not having paid taxes, fees, premiums, or other required payments by the due date. A formal/administrative term.
税金が未納になっている。
Taxes are unpaid.
保険料の未納が続くと、保障が受けられなくなる。
If non-payment of insurance premiums continues, you won't be able to receive coverage.
家賃の未納が3か月以上続いた場合、契約解除となることがあります。
If rent remains unpaid for more than three months, the lease may be terminated.
Part of the 未～ (not yet) prefix pattern: 未納 (not yet paid), 未払い (unpaid), 未着 (not yet arrived). Common collocations: 税金の未納 (unpaid taxes), 未納分 (unpaid portion), 未納者 (non-payer). Distinguished from 滞納 (delinquent payment) — 未納 is neutral and simply means 'not yet paid,' while 滞納 implies willful non-payment or default.