Struggling families fork out £16milion extra a year for their TV licences because they choose to pay in quarterly chunks, a top BBC executive admitted.
Hard-up households who try to spread the £144.50 annual cost over four manageable instalments pay a £5 penalty every year, MPs heard.
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The corporation reaps a huge bonanza from what it calls "a small premium of £1.25 per quarter", the Commons Public Accounts Committee was told.
Pipa Doubtfire, head of revenue management at the corporation's licence fee unit, said: "It goes straight into the consolidated fund as all other monies collected, and it's about £16million per annum."
Shocked committee chairwoman Meg Hillier said simply: "Wow."
That would equate to about 3.2 million households being hit with the penalty for paying in four instalments.
Meanwhile, an internal investigation into licence fee enforcement uncovered no evidence of "systemic" shortcomings, an executive of the company carrying it out on behalf of the BBC told MPs.
Capita group operations and performance director Vic Gysin admitted footage and transcripts of enforcement officers obtained by a newspaper made "unedifying" viewing.
But he denied officers were given financial incentives to drive up numbers of prosecutions, saying performance bonuses were linked to success in persuading households to sign up to payment schemes.
BBC director general Lord Hall last month demanded "urgent clarification and reassurance" from Capita that vulnerable people were not being targeted following claims enforcement officers were ordered to catch 28 evaders every week and promised incentive bonuses of up to £15,000 a year.
Capita reportedly earns £58million a year from the BBC to collect licence fees.An undercover journalist who applied for a job with the company reported being told to persuade householders to hand over cash or card payments on the doorstep.
Among those pressed to pay up were a war veteran with dementia and a single mother in a refuge, it was claimed.
Mr Gysin told MPs two officers remained suspended pending an internal probe, expected to end in two weeks.
"The results we have had back so far do not indicate that this is a systemic issue," he said.
"We have over 300 people in our field team. None of them are actually incentivised to tackle evasion as such.
"They don't undertake prosecutions, they take records of interviews on the doorstep. They are purely incentivised on revenue collection."
Enforcement officers earn about £20,000 a year but trouser £9,000 in commission for racking up doorstep "sales" of licences.
Officers were able to accept payments of as little as £5.60 towards a licence but commission may not be triggered until households built up a pattern of making payments, the committee heard.
The Capita executive admitted the company was about 50 officers short of its internal target of 380, blaming anti-social hours and "unpleasant" encounters with licence fee dodgers.
Some 99 officers were assaulted over the past year, with some ending up in hospital, he said.