I like the graph available on the dashboard showing the sales for the last 12 months although I do believe that a graph (separate or a individual line on the same graph) showing the 12 month accumulated sales would be useful in being able to quickly see if the user has gone over the VAT threshold. And possibly being able to go back to a specific dates to see when someone went over the threshold.
At the moment I'm spending time adding up each month from a sales report which can be time consuming.