> ## Documentation Index
> Fetch the complete documentation index at: https://docs.orbit.devotel.io/llms.txt
> Use this file to discover all available pages before exploring further.

# The billing model map: four wallet/usage pages, one index

> Which of the four overlapping money pages owns which question — the wallet-ledger family, the pause/gate chain, the rate-resolution family, the money-adjacent pages, and a 'which page owns' table for the questions readers ask most.

# The billing model map

Four concept pages describe the same prepaid-money arc from different
angles, and until now nothing said which one to open for a given question.
This page is that index. Resolve your question here, then jump straight to
the page that owns the answer — without reading four pages to find the one
rule you came for.

## The four billing-concept pages, one question each

| Owner page | The question it answers in one sentence |
| - | - |
| [Wallets, credits, and charges](/concepts/wallets-credits-and-charges) | How does money move on the wallet ledger — the append-only credits and debits, the pause flags, the idempotency keys, and the unit representation every balance is carried in? |
| [Usage metering pipeline](/concepts/usage-metering-pipeline) | How does a send become a usage record and then a rollup — where metering ends and billing begins, and why every figure can be re-derived? |
| [Billing and wallet](/concepts/billing-and-wallet) | How is a usage event rated — the rating pipeline, included-quantity and graduated-tier pricing, the FX source pipeline, tax, and authorize-before-use? |
| [Usage records model](/concepts/usage-records-model) | What is the row-level billing feed — one record per sent message or completed call with the billed units and price each debit was computed from, and how do you reconcile it? |

Everything else on the money arc — the pause and gate chains, the
rate-resolution family, the documents and attribution pages — hangs off
those four. The rest of this page maps each of them onto the family it
belongs to and puts a "which page owns" table at the bottom for the
questions readers actually confuse.

## The wallet-ledger family

* [Wallets, credits, and charges](/concepts/wallets-credits-and-charges)
  is the ledger itself. It owns the append-only credit/debit model, the
  pause bits that gate outbound sends, the idempotency keys that make a
  retried debit safe, the integer micro-cent units every balance figure is
  stored in, and the degraded-balance fallback.
* [Usage metering pipeline](/concepts/usage-metering-pipeline) owns the
  send → usage record → rollup chain end to end. It also owns the
  metering-vs-billing boundary (metering measures; billing prices) and the
  re-derivation guarantee — every rollup can be replayed from the raw
  records.
* [Billing and wallet](/concepts/billing-and-wallet) owns what happens to
  a usage event when it crosses that boundary: the rating pipeline that
  prices it against included quantity and graduated tiers, the FX source
  pipeline for converted top-ups, tax handling, and the
  authorize-before-use contract.

Read these three in that order when you are onboarding onto the billing
surface; the fourth page of the family, [usage records
model](/concepts/usage-records-model), is the reconciliation lens back
down to row level.

## The usage-record → rollup → invoice chain at a glance

1. A send completes (message out, or a call ends). Metering writes one
   append-only usage record with the billed units.
2. The rating pipeline prices the record against the resolved rate and any
   tiers or surcharges in force.
3. Rollups aggregate the priced records into the figures the invoice or
   statement is built from.
4. The invoice (billing provider) or statement (wallet ledger) renders
   from those rollups — see
   [billing documents model](/concepts/billing-documents-model).

The owner for steps 1–3 is [usage metering
pipeline](/concepts/usage-metering-pipeline); the owner for step 4 is
[billing documents model](/concepts/billing-documents-model). The
row-level feed underlying step 1 is [usage records
model](/concepts/usage-records-model).

## The pause/gate chain family

Balance-driven pauses and account-lifecycle holds are deliberately
separate pages; the chain they both sit in has its own page.

* [Billing gate chain model](/concepts/billing-gate-chain-model) — the
  ordered chain every outbound send walks before funds move: pre-flight
  balance check, pause/block flags gate, per-channel fund path, atomic
  check-and-decrement. Per-surface zero-balance behavior lives here.
* [Outbound pause and the free-channel
  exemption](/concepts/outbound-pause-and-free-channel-exemption) — why a
  balance-driven pause bypasses \$0-price channels like WhatsApp while an
  account-lifecycle hold blocks every channel.
* [Two-phase billing lifecycle](/concepts/two-phase-billing-lifecycle) —
  the authorize / capture / release lifecycle for flows that reserve funds
  before they run, versus the synchronous charge path.
* [Committed-use drawdown
  model](/concepts/committed-use-drawdown-model) — the enterprise monthly
  commitment meter: where the commitment lives, how to read the drawdown
  and run-rate projection, and why the meter degrades to a hidden panel
  instead of an error.

## The rate-resolution family

Every rating decision resolves through one precedence ladder. The main
ladder page and the layer-specific pages are:

* [Pricing and rate resolution](/concepts/pricing-rate-resolution) — the
  SMS price precedence ladder: a verbatim per-operator override ahead
  of organization markup ahead of the platform-default markup, plus the
  no-published-rate case.
* [MCC/MNC override model](/concepts/mccmnc-override-model) — the
  per-(organization, operator) override record that binds one network to
  one fixed price, applied verbatim ahead of every markup rule.
* [Volume-tier resolution
  model](/concepts/volume-tier-resolution-model) — graduated rates that
  apply themselves at debit time from a monthly usage counter.
* [All-in pricing: surcharges](/concepts/pricing-all-in-surcharges) — the
  itemized surcharge menu (registration, recording, transcription,
  premium support) stacked on the resolved base rate.
* [What-if pricing model](/concepts/whatif-pricing-preview-model) — the
  money-free simulator that re-prices your recorded usage lanes against a
  candidate rate card. Ends where live rate resolution begins.
* [Reseller margin and the tax
  pipeline](/concepts/reseller-margin-and-tax-pipeline) — the
  per-subaccount margin applied before tax, and why it lands on ledger
  descriptors rather than the wallet.
* [Pricing-preview pipeline](/concepts/billing-pricing-preview-model) —
  the five read-only preview endpoints that project a billing period
  before it closes, and how they differ from the ledger, the invoices,
  and the what-if simulator.

## The money-adjacent family

Pages that the billing surface depends on without being part of the
rating or ledger:

* [Billing documents model](/concepts/billing-documents-model) — what
  invoices, statements, and recurring-agent subscriptions each mean, and
  why statement balances reconcile through the wallet.
* [Spend anomaly and alert
  model](/concepts/spend-anomaly-and-alert-model) — threshold alerts,
  burn-rate projection, and automatic velocity-anomaly detection, with
  the anomaly ledger behind them.
* [Cost channel rollup model](/concepts/cost-channel-rollup-model) — why
  the Insights "Costs by channel" totals legitimately differ from the
  ledger totals, and how to reconcile them per period, channel, and
  currency.
* [LLM spend cost attribution
  model](/concepts/llm-spend-cost-attribution-model) — the feature ×
  model × conversation attribution axes behind the AI-spend surfaces and
  the conversation P\&L view.
* [Billing API reference](/api-reference/billing) and the [usage metering
  API reference](/api-reference/usage-metering) — the endpoint-level
  surface for wallets, usage records, and rollups. Concept pages explain
  the model; the API reference names the endpoints and fields.

## Which page owns the question? The five most-confused cases

| Question | Owning page |
| - | - |
| My send was refused with a 402 — what gate rejected it? | [Billing gate chain model](/concepts/billing-gate-chain-model) |
| Which precedence does a per-operator override versus an org markup take? | [Pricing and rate resolution](/concepts/pricing-rate-resolution) |
| Why does a zero balance still let WhatsApp sends through? | [Outbound pause and the free-channel exemption](/concepts/outbound-pause-and-free-channel-exemption) |
| Where do I reconcile a wallet debit down to the billed units and price? | [Usage records model](/concepts/usage-records-model) |
| Insights costs by channel disagree with the ledger — which one is right? | [Cost channel rollup model](/concepts/cost-channel-rollup-model) |

Ledger idempotency keys belong to [wallets, credits, and
charges](/concepts/wallets-credits-and-charges); pause semantics belong to
[the gate chain](/concepts/billing-gate-chain-model); usage metering as a
pipeline belongs to [usage metering
pipeline](/concepts/usage-metering-pipeline); and rating belongs to
[billing and wallet](/concepts/billing-and-wallet). If your question is
not in the table, pick the family above and open the page whose one-line
question matches yours.

## See also

* [Billing and wallet](/concepts/billing-and-wallet) — the rating
  pipeline end to end
* [Wallets, credits, and charges](/concepts/wallets-credits-and-charges)
  — the ledger mechanics
* [Usage metering pipeline](/concepts/usage-metering-pipeline) — send →
  record → rollup
* [Usage records model](/concepts/usage-records-model) — the row-level
  feed
* [Billing documents model](/concepts/billing-documents-model) — invoices,
  statements, subscriptions
* [Billing API reference](/api-reference/billing) — endpoint-level
  surface