First and foremost, one should always consult their tax professional on questions of this nature.
It is our understanding that Heleum gains are subject to capital gains taxes, which vary by jurisdiction.
Currently, Uphold will report with a 1099-K if your transaction volume reaches a certain amount. Read more at Uphold here.
Update: Watch this webinar by Heleum on preparing taxes.
Here's a How To guide on this process, from Heleum.