Cost Centre

I use AccountRight so I can utilise the Cost Centre (previously Categories) to assign multiple sources of Government funding to each transaction. That way I can run a Cost Centre P&L and Balance sheet against each Cost Centre?

I cannot locate where I can assign the Cost Centre against a receipt or payment.

What has changed in AccountRight?  How do assign the Cost Centre field to each transaction??

Also, all previously entered transactions are displaying error messages that the GST is wrong.

Regards 

Ian