Current period usage for the calling key

True when the last subscription payment failed and the provider is still retrying. The paid allowance is UNCHANGED while this is true; only if every retry fails does the key drop to the free tier. This is the only in-band billing warning the API gives — poll it if you want to detect trouble programmatically.

Human-readable explanation, present only when past_due is true.

The ROUTE that mints a billing-portal link — not a link. Always /v1/billing/portal. Call it with the customer's own key and it returns a one-time URL where they change plan, update the card, download invoices and cancel.

It is an endpoint rather than a URL because Paddle has no static portal page: each link is a session bound to one customer and it expires, so there is nothing durable to publish here, and minting one on every /v1/usage poll would spend a live API call on a link nobody opens.

Present on /v1/usage only for keys that actually have a subscription — a free key has nothing to manage, and pointing one at a route that will answer 409 is worse than saying nothing. Absent, never null.

Present only on a key whose tier is TIME-LIMITED — today, a key minted by an Invoice Fix Report claim (POST /v1/fix/claim), which carries 30 days of starter. Published both before and after the date passes: once past, tier above already reads free, and this field is the whole explanation of why. The key itself never expires and is never deleted; only the monthly allowance changes.