The attacker, Christopher Dolan, 33, of Tayview Drive, Liff, Dundee, admitted the assault, which took place at Perth Honda on December 20 last year.
The victim, Graham Mitchell, suffered a nosebleed, swelling and bruising as a result.
Perth Sheriff Court heard that Mitchell and some of his colleagues were discussing the issue of customer discounts while Dolan was siting at a desk a short distance away.
After saying ‘I’ve had enough of this s***’ he got up and walked towards Mr Mitchell before the assault took place.
According to the Scottish TV website, solicitor Graham Harding, defending, said: ‘It was an argument that escalated and he lashed out. He has expressed genuine remorse for his actions.’
Dolan was suspended from work before resigning a few days later. He has found another job but is being paid £10,000 less a year than he was in his previous role, the court heard.
Mr Harding told the court: ‘He has lost a significant amount of income. He was a business manager and is now employed as a car salesman. He has lost about £10,000 a year.’