1. Failed payments
In the Stripe Dashboard open Billing, then Invoices, and filter by status Uncollectible and Past due. For each invoice check whether the customer still has an active subscription. If they do, they are using your product without paying.
2. Missed upgrades
Export your subscriptions with their price and compare them with your own usage data: seats, projects, API calls. Sort by usage per dollar. The accounts at the top are your upgrade candidates.
3. Discounts that never ended
Open Product catalog, then Coupons. Look for coupons with duration forever and check how many active subscriptions still use them.
4. Silent churners
Match your active subscriptions against your login or activity data. Every paying account with no activity in 30 days is at risk of cancelling soon.
5. Underpriced plans
Group active subscriptions by price. If you see many customers on prices you no longer offer, those are legacy prices still billing.
6. Abandoned checkouts
Under Payments, look at Checkout Sessions with status expired. Each one is a person who picked a plan and left before paying.