How can CSA investigate me on figures I have absolutely no idea about?

October 3, 2019

I won’t drag this out and go into the behaviour of my ex partner and lies she has told.
I am self employed as a Landscaper, earnings are hit and miss.
As a result sometime good, but mostly way below average.
Long story short, my Ex went to the CSA and as they do, they’ve been hounding me at every opportunity.
I had an August review this year and as a result my payments went to £57 per week.
One would think all is settled, but no.
Yesterday I had a letter form the CSA Finacial Investigations Unit.
Asking to explain my earnings fro 2016 to 2017.
They have figures listed of what I’m supposed to have earned that year.
Which I find totally baffling as I had’nt entered a tax return as I had no earnings in that period other than a minor pension draw down.
I’ve not responded as yet, but how can they investigate me on figures I have absolutely no idea about.
I’m wary to respond without advice as everyone knows they are like a dog with a bone and won’t let go.
Any ideas/advice please.