Hi there, alice-toh-zb.
If you're on a trial version of QuickBooks Online, then you can subscribe to the plan by updating your billing information.
Here's how:
- Sign in as the Master or Company Admin.
- Go to Settings > Account and Settings > Billing Subscription.
- Select the pencil icon beside your payment method and update your credit card information.
- Make sure the address in QuickBooks matches the one on your credit card statement.
- Select Confirm card or Save.
I've got this article for reference: Update the payment information for your subscription.
If you have QuickBooks Desktop in the U.S version and want to register the program, you can check out this article for additional details: Register QuickBooks Desktop using Intuit Account.
When prompted for the validation code, I'd recommend contacting our Customer Care Team by following these steps:
- Click Help located at the top.
- Choose QuickBooks Desktop Help.
- Enter a brief description of your issue and click Continue.
- You can choose Message an Agent or Talk to a Specialist.
Please know that we are always around to help you if you need anything else. Thanks.