> For the complete documentation index, see [llms.txt](https://docs.tiun.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tiun.io/reference/checkout/one-time-purchases.md). # One-time purchases A one-time purchase in tiun ties an **identified user** to a **product** through a **single payment**. This page covers the lifecycle from anonymous visitor to paying customer — and why, unlike a subscription, there is nothing after that to manage. *** ## The journey 1. A **visitor** arrives unauthenticated — no tiun session yet. 2. They open **checkout** directly. The overlay collects email and payment; completing it **authenticates the user** and **grants access** to the product in one step. 3. Alternatively they may **log in first** with `tiun.login()`, then buy later via checkout when ready. 4. A **returning user** on the same browser gets **session restoration** automatically; `userChange` fires with `event: 'init'` so your UI can sync. 5. The user may **log out**; the session is cleared and they're anonymous again until they sign in again. Logging back in restores the purchase. {% hint style="info" %} Checkout authenticates the user automatically. If a visitor goes directly to checkout without logging in first, they provide their email during the payment flow and are authenticated as part of completing it. {% endhint %} *** ## Access is permanent A one-time purchase is charged **once**. There is no billing cycle, no renewal, no cancellation flow, and no expiration. Once checkout completes, the product ID is added to the user's `productAccess` and **stays there** — across sessions, logouts, and new devices, for as long as the account exists. Your gating code never has to handle revocation for a one-time product: if the ID is in the array, the customer has paid for it. See [Product access](/reference/checkout/product-access.md) for how that array is populated and how to check it in code. {% hint style="info" %} Because access can't be cancelled, you can't reset a one-time purchase for a test customer. To re-test a first-purchase flow in sandbox, run checkout with a **new email address** — see [simulating payments](/guides/testing/simulate-payments.md). {% endhint %} *** ## Bought once per customer The same customer can't buy the same one-time product twice. tiun stops the repeat purchase before any money moves, in both directions it can be attempted: * **Signed in and already entitled** — checkout links the existing entitlement instead of charging again, and the customer sees an "already purchased, no new charge was made" screen. * **Signed out, signing up again with the same email** — the sign-up is rejected because the customer already exists. They have to log in to reach what they own. So a one-time product is a **perpetual licence, not a consumable**. It isn't a shop item that can be re-ordered: there are no quantities, carts, credit packs, or "buy another" flows. If you need customers to buy the same thing repeatedly, a one-time product is not the right model for it. Two consequences for your UI: 1. **Hide or disable the buy button once the customer owns the product.** Gate it on `productAccess.includes(productId)`. Leaving it live sends a paying customer into a checkout that cannot charge them. 2. **Put a visible Log in option on your sales page**, not just a buy button. Login is the only route back for a returning customer — signing up again with their email is rejected, so a buy-only page leaves them stuck. Copy should match the model too: "Buy", "Purchased", "You own this" — not "Subscribe", "Manage your plan", "Renews on", or "Cancel". None of those states exist for a one-time purchase. *** ## Where to go next * [Checkout / How it works](/reference/checkout/how-it-works.md) — what the overlay does and how identity is verified. * [Product access](/reference/checkout/product-access.md) — how `productAccess` is populated and how to gate features. * [Products](/reference/generic/products.md) — how the one-time product type compares to subscriptions and time-based billing. * [Authentication / How it works](/reference/authentication/how-it-works.md) — the broader login and session model. * For an end-to-end walkthrough, see [selling one-time products](/guides/one-time-purchases/sell-one-time-products.md). --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. 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