Gemini API: Prepay and Postpay Billing Plans

Gemini API Introduces Prepay and Postpay Billing Plans

As of March 23, 2026, Google has rolled out two structured billing plans for the Gemini API in AI Studio — Prepay and Postpay — replacing the previously implicit billing model with clearly defined payment options. Existing accounts may be automatically assigned to one of these plans; Google recommends that all paid developers log into AI Studio to review their billing setup.

How Prepay Works

Under the Prepay plan, developers purchase API credits in advance before usage begins. These credits are deducted from the account balance in near real-time as API calls are made, giving developers full visibility into spend as it happens.

Key details for the Prepay plan:

• Minimum credit purchase: $10; maximum: $5,000 per transaction
• Credits expire after 12 months from the date of purchase
• Credits are generally non-refundable, with one exception: if the account later switches to Postpay, any unused Prepay credits are refunded
• Available to all developers with a linked billing account, regardless of usage tier

Prepay is well-suited for individual developers, teams operating under fixed budgets, or any developer who wants a hard spending ceiling without relying solely on project-level spend caps.

How Postpay Works

The Postpay plan operates as a traditional monthly billing cycle: API usage costs accrue throughout the month and the linked payment method is automatically charged either at the end of the billing period or when expenses reach a pre-set threshold. This mirrors the billing model familiar from other cloud API providers.

Postpay eligibility requires Tier 3 status — a cumulative spend of $1,000 or more across Google Cloud services and an account at least 30 days old. Alternatively, developers can qualify through direct engagement with Google Cloud sales.

A critical constraint applies: once a billing account switches from Prepay to Postpay, that switch cannot be reversed. Developers who later want Prepay billing for specific projects must assign those projects to a separate billing account configured for Prepay.

Context: The Final Step in a Three-Part Billing Reform

The Prepay/Postpay launch is the third major billing change Google has made to the Gemini API in March 2026 alone, completing an overhaul that began weeks earlier:

• March 12, 2026: Project-level Spend Caps were introduced in AI Studio
• March 16, 2026: Google revamped the Usage Tier structure with lower qualification thresholds and automatic tier upgrades
• March 23, 2026: Prepay and Postpay billing plans took effect

This series of changes follows well-documented billing incidents from 2025, including a configuration error that caused over $70,000 in erroneous fees and a stolen API key incident resulting in an $82,000 charge.

What Developers Should Do

Developers with active paid Gemini API accounts should review their billing plan assignment in AI Studio immediately. Those who prefer budget-controlled workflows should confirm their account is on Prepay. Teams with predictable, high-volume usage and Tier 3 status may prefer Postpay.