Consequetive invoice numbers.

It seems that the invoice number is linked to the WordPress post change ID which changes every time the document is saved.

I issue my invoices sequentially: after I’ve issued invoice 309, I’m expecting to see the next invoice as invoice number 310, but instead it is 318 (for example) so I have to change the number by hand.

If I forget to do this, then I issue the Invoice as 310, but the invoice has 318 on it which confuses the client.

Is there a way of controlling the invoice number so that it increments from the last number? If not, would this be a useful feature to implement for future updates?