WBS, Standard licences purchased between 6/4 and 19/5 expire 5/4 the following year to prevent unscrupulous buyers from getting 2 years internet filing out of a 1 yr purchase. But if you let us know (after buying) that you won't be doing any 08/09 filing with the software we will extend that expiry to 365 days. As long as the expiry is 6/4 or later you get as long as you need to file for that year; you don't need to rush to get it done before expiry. Alternatively a 2 or 3 year licences automatically lasts for the full 2/3 years so then you don't need to do anything).
When you upgrade to the bureau version you automatically get credited with the remaining portion of a premium licence that you hold, so you don't lose anything by buying a premium licence now and upgrading to a bureau licence when you exceed 5 clients. The calculation of that credit is shown on the My 12Pay page (whenever you visit it) once you've purchased a Premium licence.