AN ARGUMENT over a phone bill led to a man assaulting his teenage stepdaughter and ultimately the split of the family, Toowoomba Magistrates Court heard.

The then Meringandan West-based family had been going through financial difficulties last year when a bill of $600 for the 16-year-old girl's phone arrived.

Through his solicitor, Nathan Bouchier, the man, 43, told the court he paid his stepdaughter's phone bills, which had usually been about $50 a month.

An argument arose between him and his de facto partner over the girl's $600 bill on October 31, last year, during which he had tipped over the chair on which the girl was sitting.

Police prosecutor Senior Constable Tim Hutton told the court the teenager hit her head and hip when she fell to the floor and was left with bruising.

Originally, the man had been charged with assault occasioning bodily harm but he pleaded guilty yesterday after police reduced the charge to common assault.

Mr Bouchier told the court his client had been under financial stress at the time, and since the incident he had separated from the family and moved to Mackay.

His client had only meant to scare the girl by tipping her out of the chair, he said.

Magistrate Graham Lee said the man had already suffered a penalty in having to pay the $600 phone bill, but warned that was no excuse to assault the girl.

He placed him on a 12-month good behaviour bond and ordered that no conviction be recorded.