I had to apply to have my voice removed as I was one of the those who had been harvested a few years ago in what must have been a trial run. I certainly don't remember being asked to say anything specific and voice recognition was certainly never mentioned but when I contacted HMRC last November they confirmed that my voice ID was on record and "if I insisted" it would be removed. I insisted.
Whether I opt in sometime in the future will be my decision. Good to have it confirmed that 'opting in' is being used Hugh rather than an assumption that you want to put your faith in voice recognition being infallible.
Jo pulls her aluminium hat firmly down over her ears.