When you hire a lawyer, your chances of overpaying are considerable, according to one legal expert.

“There is potentially 10% to 30% chance of legal bills for overcharging or over-inflation of hours disguised as blocks analyzing this or focusing on that,” said Ryan Loro, president of Philadelphia-based SIB Legal Bill Review, a service that monitors legal charges.

The red flag is “block billing” — a way of assigning one charge for several separate tasks.

An example of overbilling, said SIB Legal Review officials, could be a lawyer who charges $300 an hour and personally decides to make a three-hour drive to and from an off-site storage facility to retrieve records instead of delegating the task to a secretary — who makes much less.

By packaging all the work into one bill over a monthly billing period and not documenting each day’s work, some lawyers inflate bills, said SIB Legal Review VP Joe DiGuglielmo.

Block billing, he adds, can still be used, but clients should insist firms “document what they were doing each day of a billing period.”

DiGuglielmo warned that without daily documentation, some lawyers couldn’t prove “they did anything.”

The American Bar Association, which didn’t respond to requests for comment, advises members to abide by Rule 1.5(a) of Professional Conduct. “A lawyer,” the rule states, “shall not make an agreement for, charge or collect an unreasonable fee or an unreasonable amount for expenses.”

While legal professionals are most likely to overcharge, DiGuglielmo said, others, such as dining wholesalers and public relations pros, also can pad their bills.