(i) Invoice is a business document or bill or statement giving the details of goods sold as to the quantity, quality, price, total value, etc.
(ii) Thus the invoice is a source document of prime entry both for the buyer and seller. It is purchase invoice or inward invoice for the buyer and sales invoice or outward invoice for a seller

According to the Negotiable Instruments Act, 1881, "Bill of exchange is an instrument in writing containing an unconditional order, signed by the maker, directing a certain person to pay a certain sum of money only to, or to the order of a certain person or to the bearer of the instrument".

(i) A credit note is prepared by the seller and sent to the buyer when goods are returned indicating that the buyer's account is credited in respect of goods returned.
(ii) Credit note is a statement prepared by a trader who receives back from his customer the goods sold.
(iii) It contains details such as the description of goods returned by the buyer, quantity returned and also their value.

(i)  Goods returned by the customers may also be known as "returns inwards".
(ii)  Sales return book has got the same column as Sales Book.
(iii) In this book are recorded the transactions relating to goods sold on credit only.

(i) Transactions relating to previously purchased goods returned to the suppliers are recorded in a separate subsidiary book which is called purchases returns book.
(ii) Since goods are 'going out' to the suppliers, they are also known as 'returns outward' and the book is called as 'returns outward book or returns outward journal'.