Parking charges are set to be introduced at the area's mental health hospitals for the first time.
From June the public will be charged £1-a-day for any period of time they park at the hospital.
Monthly tickets can be bought for £12, allowing visitors to park any time over four weeks.
Motorists who fail to buy a ticket will receive an £85 fine, which will drop to £50 if paid within 14 days.
According to the trust it costs around £246,052 a year to maintain its car parks.
The trust has 898 spaces across the three sites, and they claim each one costs £274 a year to maintain.
SWLSTG state the money raised from parking charges will be redirected to healthcare.
Mike Naylor, deputy chief executive of SWLSTG, said: "We have to cut £35m from our overall budget in the next five years.
"This is an extraordinarily challenging target and we have to look very hard at every part of our operation in order to achieve it.
"We are absolutely determined that these financial cuts will not impact on the health and social care we provide, and although we regret having to introduce a charge, we cannot justify continuing to provide free parking.
"However, we have endeavoured to keep the fee as low as possible and our rates compare favourably with other healthcare providers."
The trust have said they will run the car parks themselves.
Healthcare trusts in other areas have come under fire for outsourcing car park management, with little of the profit going back into healthcare.
St George’s Hospital in Tooting, which is ran by the St George's Hospital NHS Trust, charge £2 an hour for parking,
The public also have to pay £12 for over six hours, and £20 for over 12 hours.
St Helier Hospital in Sutton charge £2 for the first hour, and then £1 for every 30 minutes.
However charges at the site are capped at £12 for 24 hours.
Kingston Hospital charge £1.80 for the first hour, then £1.50 an hour for up to five hours.
South West London and St George’s Mental Health NHS Trust (SWLSTG) aim to break even with their £1-a-day charge.
There is no set day in June for when the fees will be applied.