China's banks are playing a risky game: the deposit shuffle. The rules are simple. Pile billions of yuan in customer deposits onto the balance sheet in time for the financial reports, then shimmy them off afterwards.

The motivation for this "window-dressing" is simple - to make it look like the banks' loans do not exceed the regulatory limit of 75 percent of deposits. The regulatory cap on the interest rate banks can pay on deposits makes funding cheap but hard to find, so the banks are tempted to game the system.

At Bank of China, one of the big four State-owned lenders, the average of deposits reported in December and June was 6 percent higher than the daily average deposit base for the six months, which it reports separately. In the previous six months, the gap was 4 percent, the same as at Minsheng Bank in the most recent period.

Is there anything to worry about? Pseudo-deposits are a less stable source of funding than the real thing. Small banks, which are generally weaker, seem to be particularly reliant on them.

Even more concerning is the desire and ability of banks to get ahead of their regulators. In itself, window-dressing is not that dangerous, but a financial crisis is much more likely when banks decide that regulation is more of an obstacle than a help.

The author is John Foley, a Reuters columnist.