Paid capital gains tax on a business but didn't get all the money

Hi, I sold a business three years ago and paid CGT the year I sold it on the total. But, the money was to be paid in 3 nstallments, the business that bought my business had just been liquidated still owing me the final payment. If I don't get it then I've paid tax on money I never recieved, how do I get a refund on this? Thanks,

Hi,
You will need to write in to advise of this so that the charge can be adjusted. - CG14933 - Deferred consideration: ascertainable: claims that consideration is irrecoverable.
this should be sent to
HMRC PAYE & Self Assessment
BX9 1AS
Thank you.