They shouldve applied for this and therefore have a response from HMRC. But thats assuming they kept copies/the correspondence didnt get lot in the post/general incompetence.
They, or you as agent, need to ring the tax unit to confirm the position.
__________________
Joanne
Winner of Bookkeeper of the Year 2015, 2016 & 2017
Thoughts are my own/not to be regarded as official advice,which should be sought from a suitably qualified Accountant.
You should check out answers with reference to the legal position
Write to HMRC Option to Tax National Unit, Ground Floor, Cotton House, 7 Cochrane Street, Glasgow, G1 1GY. Provide as much information as to location and postcode.