Royal Ascot will not take place as a public event in June but the track are still hoping it might be possible to stage the biggest meeting of the flat season behind closed doors.
A statement issued by Ascot chief executive Guy Henderson said the decision had been taken for public health and safety reasons.
He wrote: 'We have reached the difficult but unavoidable conclusion that Royal Ascot 2020 (16-20 June) will not be able to take place as an event open to the public. This will of course be a great disappointment for everyone planning to attend.
Royal Ascot will not take place as a public event but could take place behind closed doors
'It may prove possible to run the Royal Ascot races behind closed doors, dependent on government and public health policy and the approval of the BHA for us to re-start racing.
'This would be for the benefit of the industry, our valued partners and suppliers and our television audiences at home and internationally. Planning for this is now our complete focus and we will update on progress as and when we can.
'Customers who have already paid for entry and hospitality at Royal Ascot will be refunded in full in the usual way as quickly as possible and we will start the process of communicating with them, initially by email, immediately.
'We thank everyone in advance for their patience and understanding in completing this substantial task given the challenging practical circumstances of the current national lockdown.
'The pandemic will have a significant financial impact on our business in 2020, along with so many others. Nevertheless, Ascot Racecourse will come through this crisis and we look forward to being able to welcome racegoers back when it is safe to do so.'
A statement issued said the decision had been taken for public health and safety reasons