The difference between Sales book and Sales Account are:

(i) Business concerns are always profit motivated and try to increase their sales.
(ii) In order to increase the sales, they may allow a reduction in the selling price when bulk purchases are made. It is known as trade discount.

Entries in the purchases day book are made from invoices which are popularly known as "Bills".

Instead of recording in one journal, the transactions are recorded in a number of prescribed books called subsidiary books or subsidiary journals.

(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

Journal Proper is a residuary book which contains record of transactions which do not find a place in the subsidiary books such as cash book, purchases book, sales book, purchases returns book, sales returns book, bills receivable book and bills payable book.

(i) Division of work: As journal is sub-divided, the work will be subdivided and different persons can work on different books at the same time and the work can be speedily completed.
(ii) Efficiency: The sub-division of work gives same work is done by a person repeatedly, the person becomes efficient in handling it. Thus, specialization leads to efficiency in accounting work.
(iii) Prevents errors and frauds: Internal check becomes more effective as the work can be divided in such a manner that the work of one person is automatically checked by another person. With the use of internal check, the possibility of occurrence of errors or fraud may be avoided or minimised.
(iv) Saving in time: As there are many subsidiary books, work of entering can be done simultaneously by many person. Thus it saves time and accounting work can be completed quickly.
(v) Detailed informations available: As all transactions relating to a particular item are entered in a subsidiary book, it gives detailed information. It is easy to arrive at monthly or quarterly totals.

(i) Bills Receivable Book :
     (a) Bills receivable refers to Bills drawn, the payment for which has to be received.
     (b) Such bills are drawn on debtor for a specified amount payable at sign on or after specified period.
     (c) Bills receivable book contains the details of bills drawn and its disposal.
(ii) Bills Payable Book:
      (a) Details recorded in the bills payable book are the names of the parties whose bills are accepted, date of the bills payable, due date, amount, etc.
      (b) The individual accounts of the parties whose bills are accepted will be debited with the corresponding amount in the bills payable book.

The important features of a bill of exchange are as follows :
(i) It is a written document.
(ii) It is an unconditional order.
(iii) It is an order to pay a certain sum of money.
(iv) It is signed by the drawer.
(v) It bears stamp or it is drafted on a stamp paper.
(vi) It is to be accepted by the acceptor.
(vii) The amount of the bill is paid to the drawer or the endorsee.

The advantages of maintaining subsidiary books can be summarised as under :
(i) Proper and systematic record of the business transactions : All the business transactions are classified and grouped conveniently as cash and non cash transactions, which are further classified as credit purchases, credit sales and returns etc.
(ii) Convenient posting: All the transactions of a particular nature are recorded at one place, i.e., in one of the subsidiary books. For Example: All credit purchases of goods are recorded in the purchases book and all credit sales of goods are recorded in the sales book.
(iii) Division of work: As journals are sub-divided, the work will be sub-divided and different persons can work on different books at the same time and the work can be speedily completed.
(iv) Efficiency: The sub-division of work gives the advantage of specialisation. Thus specialisation leads to efficiency in accounting work.
(v) Helpful in decision making: Subsidiary books provide complete details about every type of transactions separately. Hence the management can use the information as the basis for deciding its future actions.
(vi) Prevents errors and frauds: Internal check becomes more effective as the work can be divided in such a manner that the work of one person is automatically checked by another person. With the use of internal check, the possibility of occurrence of errors or fraud may be avoided or minimised.
(vii) Availability of requisite information at a glance : The maintenance of subsidiary books helps in obtaining the necessary information at a glance.

Note: The transaction of Cash sales on April 24 should not be recorded in this book.