Oddly in August "Sebastian" is saying it is a legal requirement, however this from the Bali Sun two weeks ago:

QUOTE

Two of the most frequent criticisms of the policy are that there has been no detailed budget set out explaining how these tax funds will be spent and that the improvement outlined in the policy document are set to be realised.

The second is that in the absence of any punishment for not paying the fee, tourists have little incentive to make the contribution, whether it is a legal requirement or not.

UNQUOTE

https://thebalisun.com/tourists-must...s-high-season/