A person who intends to pay a national tax may, if the tax amount does not exceed the amount specified by Ministry of Finance Order and any of the following items applies, entrust the payment to a payment agent (meaning a payment agent prescribed in paragraph (1) of the following Article; the same applies hereinafter in this Article):
where the person intends to pay based on a payment slip prescribed in Article 34, paragraph (1) (Procedures for Payment) that is specified by Ministry of Finance Order;
第三十四条第一項（納付の手続）に規定する納付書で財務省令で定めるものに基づき納付しようとするとき。
where the person intends to pay based on a notice to a payment agent given using an electronic data processing system that is specified by Ministry of Finance Order.
電子情報処理組織を使用して行う納付受託者に対する通知で財務省令で定めるものに基づき納付しようとするとき。
In the cases listed in the following items, the provisions on postponement of tax payment, payment in kind and accessory tax apply by deeming the national tax prescribed in the relevant item to have been paid on the day specified in that item:
where a person who intends to pay a national tax has delivered to a payment agent money equivalent to the tax amount to be paid, together with the payment slip referred to in item (i) of the preceding paragraph: the day of the delivery;
where a person who intends to pay a national tax intends to pay it based on the notice referred to in item (ii) of the preceding paragraph, and the payment agent has been entrusted by that person: the day on which the payment agent was entrusted.
略称規定第二条第一項第八号
この場合において、第三十八条第二項（繰上請求）に規定する繰上げに係る期限及び所得税法若しくは相続税法の規定による延納（以下「延納」という。）…
わかりやすく言うと
所得税法または相続税法の規定により、納めるべき税金の納付を一定の期間延ばすことです。延納によって延びた期限は、法定納期限には含まれません。
定義第三十四条の三第一項・この条の中だけ
次条第一項に規定する納付受託者
わかりやすく言うと
国税の納付の事務を適正かつ確実に行えると認められ、政令で定める要件に当てはまる者として国税庁長官が指定した者で、国税を納めようとする人から頼まれて納付の事務を行う者のことです（第三十四条の四第一項）。