You can view a customer's entire transaction history by clicking on that user's profile from the CRM.
Scroll down to the Account section, where you can stop a subscription (which includes the option of canceling access immediately or at the end of the payment period) and offer a pro-rated refund.
You can also manually refund (or partially refund) any single payment as well as issue receipts for any past transaction.
Note: Pico refunds the application fee associated to payments (pro-rated for partial refunds), but Stripe fees are not returned, so the fees to cover Stripe's portion of what is refunded to users will come from the community's connected account funds. For more information on application fees: