There are four of them at this time:
March US Price Drop Sale: Tales of the Queendom of Maadre (Mar 21 2019 – Mar 25 2019)
500 Under $5 sale in Australia and New Zealand. The sale will run from March 29th- April 1st (inclusive): Body Switches
March 40% off VIP Sale (Kobo VIP members only): The Fern and The Cross and Angelica, Scholar (Mar 27 2019 – Apr 1 2019)
Linking to the US site, hoping it redirects you to the correct one.