where do i find add unique number on invoice toolbar

[santini]

i copied an older version of a office invoice (village software) from my
wifes computer and i need to add a unique number to this invoice and whe i
click on a red mark next to INVOICE it says - if you want to add a unique
number to this invoice, click the add a number button on the invoice toolbar.
i need to do this for making invoices for VAT purposes - thanks

 

[Bob I]

Instead of "copying" the software, install it, so it puts those custom
features in the right places.