Issuing invoices with no tax

InvoiceOcean allows for issuing invoices without tax, in order to do this you will have to navigate to:

 Settings > Account settings > Include VAT tax on invoices, and uncheck the box.

Please note that this will disable tax on all new invoices. Alternatively, you can simply create a new invoice and in the Invoice Entries simply disable tax. This will allow you to issue a single invoice with no tax.