To refund the last payment and end their access, use the ⋯ on their row in your dashboard. Any other refund is in your own Stripe dashboard; a full refund takes the role off and ends the subscription, a partial one changes nothing.
Their last payment, while ending their access: on your flatpass dashboard. Press the ⋯ at the end of their row in the member list, choose Cancel immediately and tick “Also refund the last payment”. The dialog shows the amount before you confirm.
Anything else: in your own Stripe dashboard, under Payments — an older payment, part of one, or a refund that keeps the member. The member paid you directly, so the charge and the money are on your account and there is no flatpass balance to take it out of. You do not have to tell us afterwards: flatpass is subscribed to refunds on your account and acts on what Stripe sends.
In full. The Discord role comes off and the subscription is cancelled, so the next renewal cannot charge them again and quietly hand the role back. Nothing is left for either of you to tidy up.
In part. Nothing changes. The role stays, billing carries on, and the next payment is taken as normal. If you meant to end the membership as well, refund the rest or ask them to cancel.
A switch’s charge. A member who moves up to a dearer tier pays the prorated difference at once. Refunding that charge in full gives the difference back and leaves them on the tier they switched to; it doesn’t end the membership. How switching works.
A fixed-date offer. There is no subscription to cancel: a full refund takes the role off and frees the buyer’s place, and a partial one keeps their access to the end date. How fixed-date offers work.
If a member disputes the charge with their bank instead of asking you, the role comes off straight away and is blocked from being re-applied while the case is open — running /membership will not put it back. Win the dispute and the role returns; lose it and the membership ends.
That is theirs to do rather than yours, and it is a different thing from a refund. Send them to how do I cancel my membership? — the short version is /membership in your server, then Manage billing, and the role stays until the period they have already paid for runs out.
Ask in the flatpass Discord, or email support@flatpass.io. Both are read by the people who build it.