When is something a 'change of circumstances' for PIP?

Hi

I have enhanced rate for both mobility and daily living.

I am autistic and have long covid.

I am extremely fortunate that my functioning is very very gradually improving thanks to some new treatments and therapies.

What I can't work out is when a gradual improvement becomes a change in circumstance. I have natural fluctuations in my condition so I don't know what timescale to use when checking the 'more than half the time' rule.

Some days I am exactly like I was when I made my original claim. BUT I've noticed over the last six months that my bad days aren't quite as frequent or severe and my good days are happening more often and significantly better. It is also true that some things I put on the original claim are no longer accurate - although I don't think there is a difference in points between what I could do and what I can now do for 51%+ of the time.

Is there an objective test I can use to work out when and how to make a 'change of circumstances' declaration?

I'm terrified for doing it because I had such a breakdown in my assessment that they had to terminate it and the Clinical Lead switched it to a paper assessment. But equally, I don't want to fail to declare something if it meets DWP criteria for a change of circumstance.