什么是Clean collection？什么是D/P，D/A？

Clean collection光票托收
The payment of a draft by the buyer on a sight basis or acceptance of a draft and payment on the due date. This type of collection can also be used with cheques. No other financial or transport document accompanies the collection.（买方对汇票即期付款或承兑到期日付款，这种类型的托收也可以与支票一起使用。收款时没有其他融资或运输单据。）

A clean collection will involve the collecting/presenting bank presenting a draft to the buyer for payment or acceptance or presenting a cheque for payment, without invoices, transport or other documents.
1.If payable at sight, the collecting/presenting bank will transfer the funds to the remitting bank, normally via SWIFT .
2.If payable at a tenor other than sight, the collecting/presenting bank will advise the remitting bank, and the accepted draft will be handled according to the collection instruction, ie hold it until maturity and present it to the buyer for payment, or return it to the remitting bank for re‑presentation shortly before the maturity date.
3.If unpaid or unaccepted, the instructions to protest, if applicable, should be carried out pending further instructions.

Documentary collection for payment on D/P terms
The payment at sight by the buyer against release of documents.

Documentary collection for acceptance on D/A terms
The acceptance of a term draft by the buyer against release of documents.

来自CITF2021， 8.1 Basic principles