Guidance Required on Selecting reCAPTCHA Billing Tier in Google Cloud

You do not need to take any action to move between the tiers other than enabling billing. Please see the following docs https://docs.cloud.google.com/recaptcha/docs/billing-information#how-it-works

Your billing status and usage volume automatically determine your reCAPTCHA tier. The following rules allow your reCAPTCHA tier to adapt to your needs:

1. When you create a new key in a project that does not have billing enabled, you are automatically put in the Essentials tier, which gives you 10,000 free assessments each month with a basic set of features.
2. When you enable billing on your project, you are automatically upgraded to the Standard tier, which gives you 10,000 free assessments each month with an advanced set of features.
3. When you pass 10,000 assessments each month in the Standard tier, you are charged a flat $8 that covers your usage up to 100,000 assessments.
4. When you pass 100,000 assessments each month, you automatically transition to the Enterprise tier, where you are charged $0.001 for each assessment over 100,000.

High-volume users, contact Sales to discuss a subscription with volume discounts.