> ## Documentation Index > Fetch the complete documentation index at: https://docs.axioniclabs.ai/llms.txt > Use this file to discover all available pages before exploring further. # Billing > Understand how Spectra charges for inference and training usage, how to add credits through Stripe, and the private-model storage limits for each account tier. API calls require at least **$0.50** in balance. Starting a training run requires at least **$5.00** in balance. ## How billing works Spectra deducts credits for inference activity and for fine-tuning runs. The Billing page shows your current balance, recent usage, invoices, and your current private-model allowance. ## Paying for Spectra * **Top up credits** with a one-time Stripe checkout payment from **$5 to $500** * **Subscribe to a monthly plan** if you want recurring credits and a higher private-model allowance * **Open Stripe portal** to update payment methods, switch plans, or cancel a subscription Subscriptions renew automatically until you change or cancel them in the Stripe portal. ## Private model limits Current limits in the product are: * **Standard account**: up to 3 private models * **Starter**: up to 10 private models * **Pro**: up to 50 private models The Billing usage panel shows the stored-model count for your current account tier. ## Invoices and payment history Past payments appear in the invoice table. You can download invoice PDFs from the Billing page, and the Stripe portal provides the full payment-management flow.