Portsmouth have been issued with a winding-up petition by HM Revenue and Customs.
HMRC sources have confirmed to Press Association Sport that the petition over an unpaid tax bill, which the club's administrator says is £1.6million, has been sent to the troubled npower Championship club.
"Ensuring tax is paid on time should be at the centre of a football club's business strategy just like any other business," said an HMRC spokesman.
"Anyone that regards paying tax as an optional extra, or that uses tax collected from employees or customers as working capital, is potentially heading for trouble.
"While a winding-up order is a last resort, there is little HMRC can do for a business - be it a football club or not - whose viability is dependent either on not paying the UK taxes to which they are liable, or on special treatment not available to other customers with similar tax affairs."