There are some S-Corporations specific rules that have to be followed, and here are some of them:
Distributions, generally, have to be proportionate to shareholder's ownership interests. For example, in 50/50 ownership scenario, each shareholder's distribution must be 50% of the total distribution. In other words, one can't take more than the other, otherwise, distributions may need to be equalized. This is something that is different for partnerships where partners enjoy better flexibility with distributions and beyond.
Also, with S-Corporations, generally, shareholders are required to compute stock and debt basis. There are nuanced debt restoration rules that shareholders must follow. It can get complex quickly where shareholders are planning to inject funds into the S-Corporation not sure best approach to go about capital contribution v. shareholder loan. Typically, capital contribution could be better, however, there are situations where shareholder loan is better to inject in and then take it out. It is case-by-case.
In addition, with Accumulated Adjustment Account (AAA) reporting, distributions cannot make AAA go below zero or cannot increase negative balance.
Finally, reasonable compensation can be at issue. For example, if it is a service corporation, let's say a law firm, where shareholders earn revenue by providing professional services to clients, and their S-Corporation reports no compensation to lawyers, rather, they take distributions out, it could be a problem. Technically, they are taking tax-free distributions, assuming no basis limitations without paying payroll taxes. The IRS has the authority to reclassify payments made to shareholders from non-wage distributions. If this is to happen, there is a great chance that interest and penalties may be accessed.