Version 4 of SliQ Invoicing makes it easy to add a follow-up note to an invoice. To add a note, simply select the invoice in the main list on the Invoices & Payments tab and then near the bottom of the main screen select the Notes tab and enter your follow-up note, e.g. you might enter something like ...
Make sure goods dispatched by 12th August
SliQ will then show the first line of the notes in the main Invoices & Payments list. Working out which invoices need following-up is them simply a matter of looking in the list to find any invoices with notes set.
Note that SliQ only shows the first line of the note in the list. This means that you can still add notes against an invoice but if you leave the first line of the notes blank, nothing will appear in the list looking like a follow-up notice.