Left over profit/(loss) is taxable/(deductible) to the shareholders in the year earned regardless of when the cash is distributed or taken out. The corp files its tax return form 1120s and attaches a form 1120s-k1 for each shareholder showing the profit or loss and any other tax attributes being passed to each shareholder. Form 1120s-k1 is also given to each shareholder (like a w2) and shows the shareholder what is taxable and instructions for where to put the numbers on their 1040.

If the shareholder does not take the profits out, because the corp needs the money to operate, the profit is kept track of in a so called "AAA" account (in the equity section of the balance sheet because its owed to the shareholder) and can then be taken out as tax-free "cash distributions" anytime so desired because the shareholder has already paid taxes (or will pay taxes) on the money. no big deal.