for unverified account (not linked to external wallets) applicable to PC only:
go to: brave://rewards/ —> View Statement
it will not be empty and shows record of past months.
example:
or for unverified account (not linked to external wallets) applicable to android and PC:
go to: brave://rewards-internals/ —> Promotions Tab
and all claims you made will show there, just look for the right date though.
example, here’s mine matching the first example above (PC):
from my phone (more records below not shown):
Unfortunately, for verified/linked accounts, the records only show on the external wallet side. Maybe, devs will allow us to see those maybe not… cross fingers.