How to select top slicing in Tax Return

JimbotheFirst

Hello
On this years' return, I have a Life Insurance policy surrender gain which takes me into the higher rate by around £3k,  The value is 12292, so notional tax of 4916, over 27 years.  However, the top slicing relief is given as only £0.01!  I seem to recall an option for this relief when I was completing the return and, in my ignorance, possibly selecting 'No'.  I have crawled back through the return, but now can't find the option question.  I could try deleting the return and starting anew to see if this helps (most of the chore is collating the data, so not a big task to re-input).

But firstly, can anybody advise on this topic please.