Tax relief on subscription - how many years back?

[rfisher]

An organisation that I subscribe to has been claiming 20% tax relief on my subscription and charging me this amount extra assuming that I was claiming this back in my annual tax return.

I wasn't.

This has been going on since 2014.

Can I claim the arrears back in my 2018-2019 return?

They won't return it as they have already claimed the relief amount.

[rfisher]

To get more money I presume.

I don't really understand WTF they are doing but I presume that it's legal.

I just need to know how many years back I can claim tax relief on the subscription.

Then I'll worry about how.

It's not the Masons btw.