Data sharing

[Kellybar]

1.  
• Does an unlimited plan accumulate unused data to share, or is sharing only for capped-data plans?”
•  

[daveNOS]

@Kellybar Unlimited plans do not use the piggybank, only capped plans can rollover data. 

[PandJ2020]

If you think about it any 'unused' data from an unlimited plan would also be unlimited...  (Which is why it does not accumulate in your piggybank)

Also, 'unlimited' isn't unlimited - it has a fair usage cap of 550GB.  (And, no, you don't get any unused data short of 550GB)