MADRID, Nov 18 (Reuters) - Spain"s High Court on Thursday ruled partially in favour of Telefonica (TEF.MC) in a long-running tax dispute with the Spanish government, meaning Madrid may have to refund some 800 million euros ($909.60 million) to the telecom firm. The case relates to overpayment of corporation tax between 2009 and 2010, according to the court ruling, which was released late on Thursday. Telefonica filed the suit in 2015, claiming it was owed some 1.59 billion euros in refunds relating to tax credits. A separate court awarded the company 702 million euros plus interest in 2019. While Thursday"s ruling, which can be appealed at the Supreme Court, does not specify how much Telefonica would be owed, the amount should be over 800 million euros, discounting the previous refund from the total claim.Telefonica declined to comment on the ruling, while the Budget Ministry did not respond to a request for comment. ($1 = 0.8795 euros)