how do i activate product key without paying further

Activation should work with the product key already purchased; no additional payment is required if the key is valid and unused.

Use these steps to activate without paying further:

1. Redeem or activate using the Microsoft account
   • Go to the Microsoft account Services & subscriptions page: https://account.microsoft.com/services/ (or use the link in the article).
   • Sign in with the same Microsoft account that was used to buy or redeem the product key.
   • If the product (for example, Office Home or Microsoft 365 subscription) is listed there, select it and choose Install. When an Office app starts, sign in with that same account to activate. No new payment is needed.
2. If Office is prompting for a product key
   • When an app (Word, Excel, etc.) asks for activation, choose Sign in instead of entering a key.
   • Sign in with the Microsoft account that the product key was redeemed to. This activates Office using the existing license.
3. When a card is requested for “future payments”
   • This usually happens when trying to start or renew a Microsoft 365 subscription (trial or recurring subscription), not when redeeming a one‑time product like Office Home & Student.
   • If the goal is only to redeem a one‑time product key, use the Microsoft account Services & subscriptions page and the product key redemption page (for example, www.office.com/setup) instead of starting a new subscription.
   • After redeeming the key successfully, activation is done by signing in; no further payment details are required.
4. If the product key is blocked or invalid
   • If a message appears such as “This product cannot be activated because the product key is not valid”, the key has been blocked and will no longer work.
   • In that case, contact the seller and request a refund, especially if the key was bought separately from the software or from a third‑party marketplace.

If the page where card details are entered does nothing after selecting Save, close the browser, sign in again to the Microsoft account Services & subscriptions page, and check whether the product already appears there. If it does, install and activate by signing in, without entering payment details again.

References:

• Using product keys with Microsoft 365
• "Product key is not valid" error when activating Office