To say that on a taxation 'all costs shall be allowed except in so far as they are of an unreasonable amount or have been unreasonably incurred' seems to me to be giving the litigant a complete indemnity, shorn only of anything that is seen to be unreasonable. The litigant does not have to establish that the costs were necessary or proper, or that the costs were of a reasonable amount and reasonably incurred. Provided they are costs of and incidental to the proceedings, he is entitled to recover them, subject only to the qualification that they are liable to be reduced in respect of anything that the taxing master considers to fall within the headings 'unreasonable amount' or 'unreasonably incurred'. In a word, the difference is between including only the reasonable and including everything except the unreasonable. In any taxation there must be many items or amounts that are plainly allowable, and many others which are plainly not allowable. In between, there must also be many items or amounts which do not fall clearly within either extreme. On a party and party taxation, or on a taxation on the common fund basis, many such items may fail to be allowed; on a taxation on an indemnity basis, they will all be included.
I do not think that it would be right to express this difference in terms of the burden of proof being shifted from the winner to the loser, though no doubt in many matters much of the argument during the taxation will proceed on these lines. But during a taxation the taxing master sees many things which are not revealed to the party against whom the order for costs has been made, and so that party will lack some of the relevant material. Instead, it is more a question of who gets the benefit of any doubt in the mind of the taxing master. On a party and party taxation, nothing will be included unless the taxing master reaches the conclusion that it satisfies the requirement of 'necessary or proper'. Similarly, where the taxation is on the common fund basis, the taxing master will include nothing unless he considers that it satisfied the requirement of 'a reasonable amount in respect of all costs reasonable incurred'. On neither basis do the rules give the benefit of any doubt to the party in whose favour the order has been made. Nothing is included unless it satisfied the words of inclusion. The indemnity basis, as I would construe it, is the other way round. Everything is included unless it is driven out by the words of exclusion, namely, 'except in so far as they are of an unreasonable amount or have been unreasonably incurred'. I should add that in applying to an opposing party a rule intended for taxations as between a solicitor and his own client, I think that it is open to the paying party to take any point and make any objection which the client could have raised, had he been taxing the bill.