Before scheduling the downgrade, two requirements must be met: 1) Close all Pockets (Accounts & Cards → select each Pocket → close it). 2) Cancel your credit card if you have an active one (contact Customer Service; any outstanding balance must be paid off before closing). Once both steps are done, the "Downgrade to Base" button becomes active: 1) Go to Profile. 2) Tap Membership. 3) Tap "Downgrade to Base". 4) Confirm. The downgrade is not immediate: it's scheduled for the end of your 30-day billing cycle. Until then you remain on Plus. While pending, you can't request a new credit card, a new debit card, or create Pockets; to do so, you must first cancel the downgrade from the same Membership screen. At the end of the cycle, the debit card (digital and physical) is frozen and your account moves to Base.
