The CSA take the money after tax in theory the car reduces you allowances, 
so your partner will be K coded. This can work big time in your favour, if 
you tell the IR you have a much more expensive/gas guzzling car than you 
really do. They will set your tax rate too high, the CSA will calculate 
after tax. But at the end of the year when they get your P60 from your 
employers the IR will realise you have paid too much tax and give it you 
back, unlike the CSA when they make a mistake. The CSA will be none the 
wiser. This works as long as you can afford to pay the tax, you can even 
tell the IR you have a mobile phone, private health care, petrol card all 
these increase your tax and reduce your CSA.

Jon
"Claire Rand"  wrote in message 
news:_fmdnfJhMdrfx5bVRVnyvgA@eclipse.net.uk...
> say other half gets a company car (its an option) this naturally counts as 
> a taxable benefit, and thus the tax take goes up, and the untaxed take 
> home goes down.
>
> q: does the csa 'cut' also go down, since its a percentage of post tax 
> income? of do they decide to count this tax take as if he was still 
> getting it?
>
> asking since if the csa can't take this into account, and have to work 
> with the post tax portion, it will be cheaper to take the car (and tax 
> hit) with a reduced csa take than to get a newer car ourselves and avoid 
> the tax hit, but keep the full csa hit.
>
> i hope the above made sense...