La Repubblica reported that 34 former MPs who left the chamber in 2013, after either failing to be re-elected or moving into the upper house, simply moved on without settling their debts at the bar.
The unpaid bills range between €300 and €800, with the combined total reaching almost €20,000.
But how could such a huge amount of debt have been racked-up in the first place?
In order to make a purchase at the bar, each MP is given a plastic card that can be topped up with cash.
However, to avoid the inconvenient and embarrassing moments when stressed-out members of parliament want to grab a quick bite but have no money on their cards, they are also allowed to go overdrawn, so long as they pay what they owe back.
But it seems many of the MPs never did.
After discovering the scale of the problem last week, the bar's administration finally cancelled the 34 cards which still had open accounts and compiled a report.
Now, the unpaid debts will need to be settled.
It is likely that the issue will be presented before the president of the chamber, Laura Boldrini, as soon as the MPs get back from their summer break.
The wood panelled bar at Palazzo Montecitorio is modestly priced, although the chamber's 630 MPs did grumble in 2012 when prices rose, pushing the cost of a coffee up to €0.80 and the price of a sandwich to €2.50.
Italian MPs are among the highest paid in Europe, taking home an average of €172,000 a year, according to figures from 2013.