Hi, many thanks for taking the time.
I think I've got this all wrong. I was thinking I could take my 5k and just pay it straight into my pension to avoid any taxation on it. But it seems I must first earn it, then declare it, then pay tax on it then put it in the pension and get the tax paid back via relief, albeit all locked up in my pension (which is OK). So it makes sense now, I pay the tax at basic and higher rate, then via the pension I get 40% back that way and therefore has the effect of cancelling out the tax.
Salary sacrifice is great and already do that via my usual employment. This is sideline so I'm being paid directly by customer and not as an employee of their business.
It's a bit confusing tbh, I mean, I have 5000, I pay tax on that so that's 2000 gone, that leaves me with 3000. I then have to find some other money from some where else, i.e. that 2000 to make it up to 5000 again temporarily, I then get my tax relief back via the pension account but its locked away, meanwhile I've put 2000 away of my own funds... but I think this is where you explain with the tax code system in that I'll get that refunded probably over the course of a year though I'd prefer them to just pay me back in one go