The general rule is that the seller must deliver at one time the exact quantity of goods which he has contracted to deliver. The Sale of Goods Act (Ont. s. 30; U. K. s. 30) provides: 30-(1) Where the seller delivers to the buyer a quantity of goods less than he contracted to sell, the buyer may reject them, but if the buyer accepts the goods so delivered he must pay for them at the contract rate.
(2) Where the sellers delivers to the buyer a quantity of goods larger than he contracted to sell, the buyer may accept the goods included in the contract, and reject the rest, or he may reject the whole. If the buyer accepts the whole of the goods so delivered he must pay for them at the contract rate.
(3) Where the seller delivers to the buyer the goods he contracted to sell mixed with goods of a different description not included in the contract, the buyer may accept the goods which are in accordance with the contract and reject the rest, or he may reject the whole.
(4) The provisions of this section are subject to any usage of trade, special agreement or course of dealing between the parties.
In sub-s. 4 of s. 30 of the Manitoba statute, the words "or in any particular trade or business" are added.
The words "mixed with" in sub-s. 3 cannot refer to physical confusion, but are equivalent to "accompanied by" If a portion only of the goods required to be delivered is delivered, properly packed in accordance with the contract, the buyer has under sub-s. 1 the right to reject them. If the portion so delivered is accompanied by the rest of the goods not properly packed in accordance with the contract, the buyer has under sub-s. 3 the right to reject the whole. Moore v. Landauer,  1 K.B. 73.
In the carrying out of a commercial contract some slight elasticity with regard to the quantity of goods is unavoidable. The tender of a wrong quantity evidences an unreadiness and unwillingness to perform, but only if the excess or deficiency in quantity is such as to be capable of influencing the mind of the buyer. The seller has no right to impose upon the buyer the burden of the payment of money not agreed to be paid but the excess in the quantity of goods delivered may be so trifling that the buyer is not entitled under sub-s. 2 to reject the whole.
Shipton, Anderson & Co. v. Weil Brothers & Co.,  1 K.B. 574.
If the contract is for the delivery of a specified quantity, qualified by the words "more or less" "about" or other similar words a reasonable latitude as to quantity is allowed of course subject to any definite limitation as to maximum or minimum quantity stated in the contract. Much greater latitude as to quantity is allowed in a case in which the subject matter of the contract is a complete cargo or the remainder of cargo, or a whole set or bulk lot, with an approximate statement or estimate of the probable quantity.
In re Harrison and Micks, Lambert & Co.,  1 K.B. 755; London Electric Co. v. Eckert, 1917, 40 O.L.R. 208, affirmed, sub nom. Eckert v. London Electric Ry. Co., 1918, 57 Can. S.C.R. 610; Susman v. Baker, 1918, 44 O.L.R. 39; Boston Book Co. v. Canada Law Book Co., 1920, 48 O.L.R. 238; see also 25 Halsbury, Laws of England, pp. 212-215, Chalmers, Sale of Goods, 7th ed. 1910, pp. 86, 209.
In the United States the corresponding section of the Uniform Sales Act contains the following provision in the place of sub-s. 1 of s. 30 of the Sale of Goods Act:
44- (1) Where the seller delivers to the buyer a quantity of goods less than he contracted to sell, the buyer may reject them, but if the buyer accepts or retains the goods so delivered, knowing that the seller is not going to perform the contract in full, he must pay for them at the contract rate. If however, the buyer has used or disposed of the goods delivered before he knows that the seller is not going to perform his contract in full, the buyer shall not be liable for more than the fair value to him of the goods so received.
The Sale of Goods Act (Ont. s. 31; U.K. s. 31) provides:
31- (1) Unless otherwise agreed, the buyer of goods is not bound to accept delivery thereof by instalments.
(2) When there is a contract for the sale of goods to be delivered by stated instalments, which are to be separately paid for, and the seller makes defective deliveries in respect of one or more instalments, [or fails to deliver one or more instalments, or the buyer neglects or refuses to take delivery of or pay for one or more instalments, it is a question in each case depending on the terms of the contract and the circumstances of the case whether the breach of contract is a repudiation of the whole contract, or whether it is a severable breach giving rise to a claim for compensation but not to a right to treat the whole contract as repudiated.
The rule stated in sub-s. 1 follows from the rule stated in s. 30 of the Sale of Goods Act, namely, that where the seller delivers to the buyer a quantity of goods less than he contracted to sell, the buyer may reject them. As to the general principle, see Reuter v. Sala, 1879, 4 C.P.D. 239; Honck v. Muller, 1881, 7 Q.B.D. 92. In the latter case, at p. 99, Bramwell Lj. said:
Suppose a man orders a suit of clothes, the price being £7-£4 for the coat £2 for the trousers, and £1 for the waistcoat, can he be made to take the coat only, whether they were all to be delivered together, or the trousers and waistcoat first?
In a case in which the seller agreed to deliver goods in London, ex a certain ship, to the buyer's craft alongside, it was held that the parcel of goods to be delivered was indivisible, and that the buyer was entitled to delivery of the whole parcel before the ship left the port to deliver goods elsewhere. As part only of the goods were delivered, the buyer's rights were those defined by s. 30 of the Sale of Goods Act.
Behrend v. Produce Brokers Co.,  3 K.B. 530.
The editors of Benjamin, Sale, 5th ed. 1906, p. 723, re mark that s. 31, sub-s. 2 is a striking instance of imperfect codification. Inter alia, they suggest that it does not cover the case where the seller omits to make any delivery at all. To meet this particular criticism, the words 'or fails to deliver one or more instalments," which do not appear in the original statute, were inserted in the Ontario statute.
If there is a total failure of performance by one party to a contract, the usual result is that the other party has the right to consider himself discharged from the obligation to perform on his part, and the same result usually follows lows if there is a partial, but substantial, failure to perform an indivisible contract. If, however, a contract provides for delivery of goods in stated instalments, which are to be separately paid for, it is more difficult to say what degree of failure to perform by one party will give to the other party the right to consider himself discharged.
In the leading case of Mersey Steel and Iron Co. v. Nay-lor, 1884, 9 App. Cas. 434, at pp. 438, 439, 23 R.C. 504, at pp. 516, 517, the Earl of Selborne, L.C. said:
I am content to take the rule as stated by Lord Coleridge in Freeth v. Burr, 1874, L.R. 9 C.P. 208, which is in substance, as I understand it, that you must look at the actual circumstances of the case in order to see whether the one party to the contract is relieved from its future performance by the conduct of the other; you must examine what that conduct is, so as to see whether it amounts to a renunciation, to an absolute refusal to perform the contract, such as would amount to a rescission if he had the power to rescind, and whether the other party may accept it as a reason for not performing his part.
The doctrine of repudiation must of course be applied in a just and reasonable manner. A dispute as to one or several minor provisions in an elaborate contract or a refusal to act upon what is subsequently held to be the proper interpretation of such provisions should not, as a rule, be deemed to amount to repudiation, but a deliberate breach of a single provision may, in special circumstances, and particularly if the provision be important, amount to a repudiation of the whole contract. It is also to be remembered that unless a different intention appears from the terms of a contract, stipulations as to the time of payment are not deemed to be of the essence of a contract of sale.
In re Rubel, etc. Co. and Vos,  1 K.B. 315, at p. 322; Payzu v. Saunders,  2 K.B. 581; see also Dominion Radiator Co. v. Steel Co., 1918, 43 O.L.R. 356; as to damages for non-delivery, see chapter 8, 83.
In Halsbury's Laws of England, vol. 25, p. 218, par. 377, it is stated:
The contract, so far as it applies to any particular instalment of goods, is discharged where default has been made in the delivery or acceptance of the instalment; . Accordingly the seller cannot afterwards claim to deliver the instalment, nor can the buyer demand it. This statement is qualified by the following:
The fact that the parties have silently omitted to enforce' and to require the delivery of any instalment of the goods, or have by mutual consent forborne its delivery at the contract time, is relevant, but not conclusive, to shew a mutual agreement to rescind the contract, so far as it applies to the instalment undelivered.
The qualifying statement above quoted, so far as it relates to the effect of silent omission to enforce and require delivery, was disapproved, as not being supported by the authorities, by the majority of the court in Doner v. Western Canada Flour Mills Co., 1917, 41 O.L.R. 503, 41 D.L.R. 476. As to failure to insist upon punctual delivery of instalments or concurrence in postponed delivery, see also Sier-ichs v. Hughes, 1918, 42 O.L.R. 608, 43 D.L.R. 297; Gerow v. Hughes, 1918, 42 O.L.R. 621, 43 D.L.R. 307; Adolph Lum ber Co., v. Meadow Creek Lumber Co., 1919, 58 Can. S.C.R. 306, 45 D.L.R. 579.
In the United States the corresponding provision of the Uniform Sales Act is as follows:
45.- (1) Unless otherwise agreed the buyer of goods is not bound to accept delivery thereof by instalments. (2) Where there is a contract to sell goods to be delivered by stated instalments, which are to be separately paid for, and the seller makes defective deliveries in respect of one or more instalments, or the buyer neglects or refuses to take delivery of or pay for one or more instalments, it depends in each case on the terms of the contract and the circumstances of the case, whether the breach of contract is so material as to justify the injured party in refusing to proceed further and suing for damages for breach of the entire contract, or whether the breach is severable, giving rise to a claim for compensation, but not a right to treat the whole whole contract as broken. In other words under this section the materiality of the breach, not repudiation by one party, is made the test of the right of the other party to refuse to proceed further under the contract.