Your VAT and company numbers can appear on the bottom of your invoices and estimates. It is important that these details are accurate and they can be edited at any time. If you're not VAT registered please do not put anything into this box. If there is a value in this box, the VAT will be applied throughout the system.
If you wish to set these up, you can simply go to your company settings and open the 'VAT and company numbers' section. Once you've entered your company numbers, hit 'Save'.