You have had recent sales so you cannot close your account permanently yet, it has to stay open for several months to cover any potential refunds.
You do not have to use your eBay Balance for any purchases, just withdraw any money there into your bank account, do not use your account for any future selling, then you can close you account or start the procedure.
Go to Help & Contact top left of your homepage and type in .... Close Account, follow the steps.
@bafta88