The two directions of the same rule. Which way reasonable compensation cuts depends entirely on the entity's tax treatment, and the two cases are mirror images.
In a C corporation, wages are deductible at the entity level and dividends are not, so an owner-employee has an incentive to characterize distributions as salary. 26 CFR 1.162-7(b)(1) addresses that directly: "Any amount paid in the form of compensation, but not in fact as the purchase price of services, is not deductible. An ostensible salary paid by a corporation may be a distribution of a dividend on stock." The regulation then names the pattern to watch for. "This is likely to occur in the case of a corporation having few shareholders, practically all of whom draw salaries. If in such a case the salaries are in excess of those ordinarily paid for similar services and the excessive payments correspond or bear a close relationship to the stockholdings of the officers or employees, it would seem likely that the salaries are not paid wholly for services rendered, but that the excessive payments are a distribution of earnings upon the stock." Salaries that track ownership percentages are the tell.
In an S corporation, there is no entity-level tax and distributions escape employment tax, so the incentive reverses: an owner-employee has reason to take a small wage and a large distribution. The IRS's position is that "S corporations must pay reasonable compensation to a shareholder-employee in return for services that the employee provides to the corporation before non-wage distributions may be made to the shareholder-employee." That direction, including the payroll-tax arithmetic, is treated on our S corporation pages.
The same regulation carries an underrated escape hatch for contingent pay. 26 CFR 1.162-7(b)(2) says the form of the arrangement is not decisive, and that "if contingent compensation is paid pursuant to a free bargain between the employer and the individual made before the services are rendered, not influenced by any consideration on the part of the employer other than that of securing on fair and advantageous terms the services of the individual, it should be allowed as a deduction even though in the actual working out of the contract it may prove to be greater than the amount which would ordinarily be paid." A commission or profit-linked bonus negotiated at arm's length before the work, in other words, is not made unreasonable by turning out well.
The measuring date is the arrangement date. 26 CFR 1.162-7(b)(3) supplies both the benchmark and the timing: reasonable compensation is "only such amount as would ordinarily be paid for like services by like enterprises under like circumstances," and "the circumstances to be taken into consideration are those existing at the date when the contract for services was made, not those existing at the date when the contract is questioned." That is the reason documenting the reasoning at the time an owner sets their own pay is worth more than reconstructing it during an examination.
What the IRS actually looks at. For the S-corporation case the agency describes the analytical starting point as the source of the corporation's gross receipts, split three ways: services of the shareholder, services of non-shareholder employees, and capital and equipment. To the extent receipts come from the shareholder's personal services, payments to that shareholder "should be classified as wages"; to the extent they come from other employees or from capital and equipment, payments "would properly be treated as non-wage distributions." The agency then lists factors it weighs: training and experience; duties and responsibilities; time and effort devoted to the business; dividend history; payments to non-shareholder employees; timing and manner of paying bonuses to key people; what comparable businesses pay for similar services; compensation agreements; and the use of a formula to determine compensation.
There is no percentage safe harbor. The regulation is a facts-and- circumstances standard and the IRS publishes no ratio of salary to distributions that is presumptively acceptable. Rules of thumb circulate widely and none of them has an authority behind it.