My co-op maintenance bills keep rising pretty consistently every month. Is there any way for me to find out why?

While it's standard for a co-op's costs to go up once or twice a year -- generally by an average of 2 to 3% per year, says attorney Jeff Reich -- you're right to suspect that a monthly increase indicates some kind of problem. And while there are a number of reasons your maintenance charges could be edging up, it should be fairly easy to get to the bottom of the problem, say our experts.

Your first course of action should be to contact the managing agent's accounts receivable department or property manager, either of whom should be able to address any problems with your billing.

One potential explanation: "It's not uncommon for residents who use auto-pay to receive a maintenance increase letter from management, but not make the corresponding increase to their autopay," says Thomas Usztoke of Elliman Property Management. "The resident ends up paying the new charge at the old rate, accumulating an increasing outstanding balance."

In other words, if you're accidentally auto-paying an incorrect, lower amount than you owe every month, your outstanding debt -- and the balance of your bills -- would keep going up accordingly. 

Depending on how your bills are structured, your monthly electrical costs could be a factor here, too.

"If you pay your electricity bill through your maintenance, that can fluctuate from month to month," notes says Corcoran broker Deanna Kory.

The charges could also be the result of an assessment, says, Kory, though your co-op should have notified you about that well ahead of time, or some other outstanding late fees or penalties you might not be aware of (again, something your co-op should have notified you about ahead of time).

Regardless of the reason here, the bottom line is to get in touch with your property manager ASAP so you're not stuck playing a guessing game.

Virginia K. Smith is the senior editor at BrickUnderground.com, the online survival guide to finding a NYC apartment and living happily ever after. To see more expert answers or to ask a real estate question, click here.