ecosystem: Invoice Factoring / PO Financing — reference pattern for receivables financing on Arc

[osr21]

Summary

Searched the circlefin org for any existing sample, reference pattern, or advisory covering invoice factoring / purchase-order financing on Arc (keywords: invoice, factoring, purchase order, accounts receivable, debtor, financier, working capital, trade finance — checked arc-node, arc-fintech, perimeter-protocol, arc-escrow, and org-wide). There isn't one. Given Arc's stablecoin-as-gas + CCTP + Gateway building blocks are a natural fit for receivables financing (a very common real-world commerce primitive), this seems like a documentation/reference-app gap worth flagging — similar in spirit to the PaymentEscrow advisory in #86.

We built an InvoiceFactoring contract as part of a stablecoin dApp on Arc Testnet and are sharing the design here as a possible starting point for an official reference pattern or sample app.

Design

Lifecycle:

Created → Funded → Delivered → Repaid
                             \→ Defaulted (permissionless, after dueDate)
Created → Cancelled (by sme, before funding)

Three roles per invoice: sme (raises it), financier (advances capital at a discount), debtor (owes the full face value).

Functions:

• createInvoice(debtor, token, faceValue, advanceBps, feeBps, dueDate, description) — moves no funds; snapshots feeBps into the invoice struct at creation time (see note below).
• fundInvoice(id) — financier's discounted advance is pulled and forwarded directly to the SME.
• submitProofOfDelivery(id, proofHash) — SME posts a delivery proof hash once goods/services are delivered.
• repayInvoice(id) — debtor repays the full face value; the contract atomically splits it into a financier payout (advance + fee) and an SME remainder.
• markDefaulted(id) — permissionless after dueDate if unpaid.
• cancelInvoice(id) — SME can cancel before funding.

Notable design decisions (informed by #86):

• Fee snapshot at creation, not at repayment — feeBps is stored per-invoice in the struct at createInvoice time rather than read from a mutable global rate, which avoids the "fee computed at release time" class of bug called out in security: developer advisory — 4 vulnerabilities found in common PaymentEscrow patterns when building on Arc Network #86 (Vuln feat: persistence meter, consensus tuning, TLS fix, spammer/arch docs #3).
• Non-recourse by design — markDefaulted() is permissionless after dueDate but performs no on-chain fund recovery. This is standard real-world factoring risk allocation (the financier prices default risk into feeBps up front), not an oversight — worth stating explicitly in any reference doc so ecosystem developers don't assume otherwise.

Suggested action

1. Consider an official InvoiceFactoring/receivables-financing reference pattern or sample app, alongside the existing PaymentEscrow-style advisories and sample apps (arc-escrow, arc-nanopayments, arc-p2p-payments).
2. If useful, happy to have this design reviewed/critiqued the way the PaymentEscrow pattern was in security: developer advisory — 4 vulnerabilities found in common PaymentEscrow patterns when building on Arc Network #86.

Reference implementation

InvoiceFactoring.sol: https://github.com/osr21/arc-stablecoin-dapp/blob/main/contracts/src/InvoiceFactoring.sol
Docs: https://github.com/osr21/arc-stablecoin-dapp/blob/main/docs/contracts.md#invoicefactoring

Environment: Arc Testnet (chainId 5042002), Solidity 0.8.20