Social media giant Twitter has been fined after failing to file its UK corporate accounts, Sky News has learned.
The company was due to lodge its annual accounts no later than September but has still not done so, according to Companies House .
As a result Twitter UK Ltd and its secondary company, TweetDeck Ltd, have been hit with automatic penalty charges by the Cardiff-based authority.
The penalties are set to climb if the companies continue to delay filing the accounts.
The returns are used as a basis for tax filings with HM Revenue and Customs (HMRC). There is no suggestion the companies have avoided any tax liability.
A spokesman for Companies House told Sky News: "They are both currently in default on the submission of accounts to us on their respective due dates.
"Companies House records show Twitter's accounts should have been delivered by September 30 but there is no indication this has been done.
"There is no indication at this stage when the accounts will be available but as a matter of routine we will already be in correspondence with the companies to request that they file as soon as possible."
Twitter UK and TweetDeck are wholly-owned subsidiaries of California-based Twitter Inc.
Twitter has yet to reply to Sky News with an explanation for why it has failed to lodge the accounts.
TweetDeck was started by Sheffield-educated computer programmer Iain Dodsworth in 2008 and sold to Twitter last year for an estimated £25m.
Twitter UK has three American directors, Ali Rowghani, Richard Costolo and Alexander Macgillivray, who list their address as a San Francisco office.
Mr Macgillivray is company secretary for both Twitter UK and TweetDeck. He is also general counsel for the parent firm and head of its public policy and trust department.
According to the Institute of Directors, one of the formal duties of a company secretary is to take responsibility for filing annual returns to the registrar in Cardiff.
The spokesman for Companies House added: "At this time they will have already attracted a late filing penalty in accordance with the tariff published on our website .
"Failure to provide accounts for the public record can, ultimately result in company strike off, however, we are some way from that at this stage.
"Our objective remains, as always, to get the companies concerned to file their account so that these can be made available for public access, which we hope will be a positive conclusion to our continuing correspondence."
Mr Macgillivray, who also holds Canadian citizenship, became TweetDeck's company secretary after services of the British incumbent - Complete Secretarial Solutions Ltd - were terminated in May, 2011.
TweetDeck's founder, Mr Dodsworth, had his role as a director terminated in July, 2011.
The social media giant's British operation was originally named Twitter Information Network Ltd. It was incorporated on June 1, last year but given a name change to Twitter UK four months later.
The management team of Twitter has recently prepared for an expansion of staff in its London and Dublin offices as it builds a multinational sales team for Europe.
Plans include increasing advertising revenue and a system to automatically translate tweet feeds into more than 28 languages.
It is also appointing a "media partnerships manager" to cultivate wider use of Twitter by celebrities including "athletes, actors, comedians, musicians etc".
The revelation about Twitter's filing status with Companies House comes amid increasing public furore over the tax arrangements of other US multinationals with HMRC.
MPs investigating corporate tax structures of multinational firms recently slammed Starbucks, Amazon and Google.
Last week Starbucks said it would give some £20m over two years to HMRC, even though it was not required to by law.
The move was slammed as a "gift" by critics and HMRC said: "Corporation tax is not a voluntary tax and Parliament sets out the rules and rates for businesses to follow.
"The public expects businesses to pay their fair share and HMRC will challenge, through the courts if necessary, any structures or tax payments that do not comply with the UK tax law."
Starbucks' decision followed a public outcry over its accounting procedures, whereby it paid just £8.6m in UK corporation tax despite receiving billions in revenue from more than 750 stores.
In an interview with Sky's Jeff Randall, Starbucks CEO Kris Engskov said the US coffee giant had not been profitable in the UK since it brought its brand to Britain 14 years ago.
But he admitted their 2011 US report and accounts may be wrong when they referred to the fact that the UK was making a "significant portion of the net revenue and earnings of our international operations".
It was revealed Google paid £6m in UK tax in 2011 on sales of £395m, while Amazon paid no corporation tax in the same period, despite sales of £3.3bn.