suppliers invoicing late?

is there anything you can do to crack down on suppliers sending you invoices late? Of course if you pay only upon receipt of invoice this is a cash flow benefit to the business. However if a lot of suppliers are doing so it creates a problem to prepare the management accounts etc if there are variances from PO to invoice. Is there anything one can do to discourage this practice of late invoicing? 

I suppose we could also look at the process for POs and provision to ensure these are as accurate as possible..