To hold a private market including a car boot sale you might need a Market Operator Licence.
You may not need a licence if the proceeds are used for charitable purposes or not for private gain, or the market is only for the sale of livestock, fodder or grain.
If in doubt, you can check with the Licensing Section if your particular event requires to be licensed or consult a Solicitor for independent advice.
The application form is available to download from the Documents Section of this page. The completed application from must be lodged with the appropriate fee. The fee list is available on the Civic Licensing Main Page.