Cheque for 8,000euro,what to do?

Hi All,
A friend of mine has just sold a mare. She got a cheque for 8000 for it. She is in full time employment and already is paying the top rate of tax. She really does not want to have to pay 42% on this one-off cheque. What can she do?

Is there somewhere she could get it cashed?

She would be very grateful of any advice.

We don't allow discussion of tax evasion which is illegal.