Companies won't stop making preferred payments on a whim and are considered less creditworthy when the payments stop. But if the company does stop making dividend payments to preferred shareholders, those missed payments accumulate as a liability on the balance sheet called dividends in arrears. Note that this only applies to cumulative preferred stock. If the prospectus says the preferred stock is non-cumulative, there will be no dividends in arrears.
Generally, preferred stock will trade with a higher yield than the same company's bonds to make up for having lower priority. It also can sometimes be converted into common stock at a set price.
How to calculate dividends in arrears
The first step is to find the expected dividend payment. Locate the prospectus for the preferred stock on the SEC's EDGAR website. The prospectus will state the annual dividend payment in the offering summary. You can also find more information on things such as liquidity preference and the use of proceeds (assuming you're able to keep your eyes open long enough to read it).
Multiply the annual dividend payment per share by total shares issued to find the total expected annual dividend payment.
Most of the time, the dividend will be paid quarterly. Find the quarterly expected payment by dividing the annual payment by four.
Finally, calculate total dividends in arrears by multiplying the quarterly expected dividend payment by the number of missed payments. This is the amount that must be paid out before common stockholders are issued dividends.