> ## Documentation Index > Fetch the complete documentation index at: https://docs.useunitpay.com/llms.txt > Use this file to discover all available pages before exploring further. # Credits overview > The credit-billing path end to end — track, resolve, deduct FIFO, and ledger. UnitPay is the billing engine where **dollars and credits are both first-class**. Most billing tools bolt credits on as an afterthought; here they run on the same catalog, the same subscriptions, and the same APIs as dollar billing — they're just a different way value moves out of the core. This page is the hub for the credit path: how it works, when to reach for it, and where to go next. ## Two paths, one core You model **what you sell** once and attach customers to it. From there, usage flows down one of two paths: ```mermaid actions={false} theme={null} flowchart LR USE["**Usage** — you report what happened"]:::core USE --> DOLLAR["**Dollar billing** (invoice-time)
aggregate → invoice → collect → PSP"]:::dollar USE --> CREDIT["**Credit billing** (track-time)
resolve charge → deduct FIFO → ledger"]:::credit classDef core fill:#7c3aed10,stroke:#7c3aed classDef dollar fill:#ec489920,stroke:#ec4899 classDef credit fill:#22c55e20,stroke:#22c55e ``` The difference is **when** money settles: | | Dollar billing | Credit billing | | ------------------------ | ------------------------------------------------------------------------ | ------------------------------------------------------------------------------ | | **Settles** | At invoice time — usage aggregates and is billed at the end of the cycle | At track time — the balance is deducted the moment usage is reported | | **Customer holds** | A running tab that becomes an [invoice](/documentation/billing#invoices) | A prepaid [balance](/documentation/credits/wallets-and-ledger) that draws down | | **Runs out of money by** | Non-payment of an invoice | Hitting a zero balance | | **Real-time gate** | Entitlement check | `check` against remaining balance | A single plan can do both — a dollar price for the subscription and a credit grant that refills every cycle. ## The credit path, step by step ```mermaid actions={false} theme={null} flowchart LR T["**Track** usage"]:::s --> R["**Resolve** the charge
(how many credits this costs)"]:::s R --> D["**Deduct** FIFO from open grants"]:::s D --> L["**Ledger** the deduction
(append-only)"]:::s classDef s fill:#22c55e15,stroke:#22c55e ``` Your app reports what happened — a message sent, a token consumed, an API call made — with `track`. This is the same call the dollar path uses; UnitPay routes it by how the plan is priced. See [the two verbs](/documentation/how-it-works#the-two-verbs). UnitPay converts the raw usage into a credit cost. In a credit system, each feature has a credit cost per unit — 6 premium messages at 3 credits each resolves to 18 credits. The resolved cost is deducted from the customer's open grants in [priority order, FIFO within a priority](/documentation/credits/grants-and-priority). Expiring grants are spent before permanent ones, so nothing is wasted. Every grant and every deduction is written to the append-only [ledger](/documentation/credits/wallets-and-ledger). The customer's balance is always the sum of their open grants — never a number you mutate directly. ## When to reach for credits Credits fit when the customer pays (or is granted) **before** they use, and value is consumed action-by-action: * **Recurring allowances** — "1,000 credits/month" that refill each cycle, burned per message or per action (Lovable-style). * **Prepaid balances** — "\$10 of credit" bought upfront and drawn down per token in dollars (Anthropic-API-style). See [Denominations](/documentation/credits/denominations) for the unit-vs-fiat distinction. * **Daily free drips** on top of a paid allowance. * **Metered work with an unknown cost** — reserve a budget, then reconcile. See [Reserving before you spend](/documentation/credits/wallets-and-ledger#reserving-before-you-spend). Reach for **dollar billing** instead when the customer is invoiced for whatever they use at the end of the cycle — see [Billing](/documentation/billing). You don't have to choose globally: pick per feature, and mix both on one plan. ## Explore the credit path Unit credits vs. fiat credits — and the rule never to mix them. What a grant is, the priority convention, and FIFO tie-breaks. Credit accounts, their lifecycle, and the append-only record. Refill a balance manually, automatically, or by credit package. The Quickstart: grant credits, spend them, read the ledger. Render balances, ledger, top-ups, and burn in your app.