Confirmation comes after the youth travel specialist’s Swiss parent firm filed for insolvency earlier this week.
STA had around 50 branches across the UK.
The company was founded in Australia in the 1970s.
In a statement posted on its website at around 7pm on Friday (21 August), STA said: "Due to the recent announcement that STA Travel UK has ceased trading, unfortunately our travel experts are unable to assist you at this time.
"Please be assured that if you had a previous booking with us, or hold a live booking, you will receive further communication in the coming days.
"We are sorry for the inconvenience and the limited information available to you at this time."
An Abta spokesperson said: "The news that STA Travel Limited, which was a long-standing Abta member, has ceased trading will send a shockwave through the industry, bringing to life the very real pressures that travel is under at the moment.
"STA Travel will be a name that is familiar to most people who will have used them to travel or been aware of their name on the high street, and this distressing news will sadly affect the livelihoods of hundreds of employees.
"People will have used STA Travel to book package holidays as well as individual air tickets.
"The majority of holidays sold were flight inclusive packages, which are protected by Atol and scheduled airline tickets only which should proceed as normal. Non-flight based packages will be protected by Abta.
"If customers booked a package holiday through STA Travel, and the holiday is provided by another tour operator, they will need to contact the tour operator who should be able to confirm that their booking will go ahead as normal.
"Further information for customers affected can be found at abta.com/statravel."
Earlier this week, Zurich-based STA Travel Holding AG – part of Diethelm Keller Group – said an external administrator would take over the running of the company in the next few days.
STA Travel Holding said “local day-to-day” STA Travel operations “may continue”, despite the insolvency proceedings.
In a statement, STA Travel UK added said each division’s country manager and leadership team would review the firm’s position.
STA Travel Holding blamed the Covid-19 crisis for bringing “the travel industry to a standstill”.
’Sad day for the industry’
The CAA confirmed STA’s demise on Friday, and issued advice to consumers.
CAA Atol spokesperson Andrew McConnell said: “We understand this will be concerning news for anyone who has booked to travel with the company or has had their booking cancelled.
"It is a sad day for the industry when a long established business like STA Travel Ltd ceases trading, especially one that many may be used to seeing in their towns and on their high streets.
“However, the Atol scheme exists for exactly this kind of situation and we are making arrangements so that all Atol protected customers can either continue their holiday and return home as normal, or make a claim if they are due to travel.”
