What is a Data allowance ? KH December 06, 2018 07:30 Updated Follow A Data allowance is the amount of Data included with your selected plan. Related articles What happens if I do not use all of my data allowance. Will the unused data allowance be carryovered? Can I add / Top Up Data in the middle of a month if I used all the Data allowance? How do I check my bill? Can I use the service outside Japan? Can I use tethering / Hotspot / Internet Sharing ? Comments 0 comments Please sign in to leave a comment.