For a long time, most European countries have been changing higher VAT rates for ebooks than for print books. Quite often, the print book rate is under 10%, and the ebook rate has been 20% or higher.
Now, recently this is changing for the better in many European countries, and the ebook rates are coming down. There are some complications, however: some countries require an ISBN on ebooks, other countries exclude specific types of books, etc.
Furthermore, we are based in Canada, and we file our VAT returns with one European country using the VAT MOSS system. We cannot just change a rate because we see it reported somewhere; we need confirmation that the lower ebook rate will be actually available to us to use when we file our quarterly VAT return.
The only time that we can confirm what VAT rates will be available for us to use is when we file our quarterly VAT returns. We cannot file a VAT return until the quarter has ended, and quarters end on March 31, June 30, September 30 and December 31. So, the very next day after a quarter ends is the earliest that we can check the officially-available VAT rates with the European country that we file our VAT MOSS returns with.
Specifically, this means that we can only confirm the available VAT rates on January 1, April 1, July 1 and October 1, and we update the VAT rates that we are charging shortly afterward.
So, if there is a lower rate available for a given country, and there are no unfortunate exclusions (like requiring ISBNs), then we update our VAT rate going forward at that time.
Finally, we are a Canadian startup, and we have no input into the VAT rates charged by various European countries -- we just comply with them!
(Please note that Brexit has not yet had an effect on the collective arrangement for VAT collection that applies to companies in countries like Canada; you can read our explanation of the situation here http://help.leanpub.com/en/articles/110747-why-do-book-prices-have-vat-added.)