On an attorney and own client bill of costs, a taxing master has discretion to disallow expenses where an attorney has overreached a client, been negligent or acted mala fide. An agreement on an hourly rate for counsel does not extend an open-ended invitation for unlimited hours to be spent on a case. The taxing master must ensure that expenses are normal, usual, and fall within what might have been authorized, and must not impose an unjust liability on a costs debtor. A client should not bear substantial costs arising from the attorney's own systems failures or mishaps, particularly where there was ample time to comply with court rules. A court will only interfere with a taxing master's ruling if the taxing master acted mala fide, from improper motives, failed to apply his mind, disregarded regulatory prescripts, or was clearly wrong - i.e., where the court's view differs so materially from the taxing master's that it vitiates the ruling.