The FCC at its open commission meeting tomorrow may vote to require carriers to notify subscribers when they are about to exceed their monthly service limits.

The agency says bill shock rules are needed to help customers avoid unexpected charges, but the wireless industry argues regulation over the issue is unnecessary because there are already ways for customers to monitor usage on their accounts.

If approved, the regulation will beat legislation proposed by Sen. Tom Udall (D-N.M.), who introduced a bill earlier this month that would require carriers to notify customers when they use 80 percent of their monthly limits.

CTIA has said that it is concerned such regulation “has the potential to cause customer confusion and frustration.”

The FCC’s bill shock rules were prompted by a report this spring which found that one in six cell phone users in the United States have experienced a sudden increase in their monthly bill without a corresponding change in their service plan.

The agency’s proposed regulations mirror those used by the European Union, which requires carriers notify customers when they reach 80 percent of their monthly data roaming limit.