> ## Documentation Index > Fetch the complete documentation index at: https://docs.upwell.com/llms.txt > Use this file to discover all available pages before exploring further. # Accounts payable API > The objects you touch to automate payables — what a carrier invoice, bill, and bill payment each do, and the order they happen in. **Accounts payable is money out**: making sure what you pay your carriers is accurate. Upwell's job is to audit what a carrier *actually billed you* against what your TMS *expected to owe* — and to flag the difference. The endpoint reference is alphabetical, which is deliberately neutral but doesn't tell you what belongs together. This page does. For the receivables side, see [Accounts receivable API](/api-reference/ar-overview). ## The lifecycle You push a **bill** — what your TMS says you owe a carrier for a shipment. A **carrier invoice** arrives, usually by email, or you submit it via API. It starts in `RECEIVED`. Matching links the carrier invoice to its shipment, carrier, and bill. The audit compares them and raises **exceptions** for any mismatch — a wrong amount, a missing POD, an unexpected accessorial. A clean invoice can auto-approve; otherwise a reviewer clears the exceptions. If your system owns the decision, Upwell sends you an **approval request** and waits. A **bill payment** records the money going out, with **carrier payment line items** recording which bills it covered. The invoice reaches `PAID`. ## The objects | Object | What it does | | ------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------- | | **Bills** | The *expected* payable from your TMS — the baseline the audit compares against. Owed to either a carrier or a vendor, never both. | | **Bill Line Items** | Priced rows on a bill. No list endpoint — read them through the parent bill. | | **Carrier Invoices** | The *received* payable — what the carrier actually sent. The AP entry point. | | **Carrier Invoice Documents** | The invoice scan, BOL, POD, and notice of assignment attached to that invoice. | | **Carrier Invoice Approval Requests** | A pending decision Upwell hands to your system to approve or reject. | | **Bill Payments** | The money going out. Links to bills only through its line items, never directly. | | **Carrier Payment Line Items** | Which bills a payment covered, and for how much. | | **Vendors** | A payable party that isn't a hauling carrier — a lumper service, a factor, a supplier. | | **Vendor Invoices** | Non-freight AP invoices, parsed from a standalone PDF upload. | | **Purchase Orders** | Inbound customer POs, parsed the same way and matched to vendor invoices. | **Bill vs. carrier invoice** is the distinction people get wrong most often. A **bill** is what your TMS says you *should* owe; a **carrier invoice** is what the carrier *actually* sent. Auditing one against the other is the whole point of AP. See [Core concepts](/concepts/data-model). ## Before any of this works Payables reference records that have to exist first. These aren't AP-specific, so they live in their own guide: * **Carriers** — who gets paid. Sync before bills. * **Shipments** — the load a bill and invoice both point at. * **Documents** — the upload mechanism the invoice scan and POD travel through. See [Syncing foundation entities](/api-guides/syncing-foundation-entities) for all three. ## Guides for this side Create the invoice, attach documents, record payment. Poll or subscribe to learn when matching and the audit finish. Approve or reject from your own system. Upload standalone PDFs and read the parsed records. What the audit checks and how exceptions are raised. Why an invoice is held and what clears it.