Supported Chains

Invoica is multi-chain by default. Every invoice carries its chain context, and the settlement watcher polls each chain’s native rail to detect incoming USDC transfers and auto-flip invoice status. No manual settlement, no chain-specific glue code on the caller’s side.

Newest support: SKALE Base — gasless USDC settlement, sub-second finality. Launched 2026-05-22.

All supported chains

Chain	Network ID	Type	Status	USDC contract
Base	`8453`	EVM	Live	`0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913`
SKALE Base	`1187947933`	EVM (gasless)	Live	`0x85889c8c714505E0c94b30fcfcF64fE3Ac8FCb20`
Polygon	`137`	EVM	Live	`0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359`
Arbitrum One	`42161`	EVM	Live	`0xaf88d065e77c8cC2239327C5EDb3A432268e5831`
Solana	`mainnet-beta`	Solana (SPL)	Live	`EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v`

How to specify a chain

The chain field at the top level of the invoice body determines which rail handles settlement. The response back-fills paymentDetails.paymentAddress (the Invoica seller wallet on that chain) and paymentDetails.usdcAddress (the canonical USDC contract). No separate lookup needed.

curl -sX POST https://api.invoica.ai/v1/invoices \
  -H "x-api-key: $INVOICA_KEY" \
  -H "content-type: application/json" \
  -d '{
    "amount": 0.10,
    "currency": "USDC",
    "customerEmail": "agent@example.com",
    "customerName": "agent-x402",
    "chain": "skale"
  }'

Response (201):

{
  "success": true,
  "data": {
    "id": "...",
    "invoiceNumber": 1775224117,
    "status": "PENDING",
    "amount": 0.10,
    "currency": "USDC",
    "paymentDetails": {
      "chain": "skale",
      "paymentAddress": "0x3e127c918C83714616CF2416f8A620F1340C19f1",
      "usdcAddress": "0x85889c8c714505E0c94b30fcfcF64fE3Ac8FCb20"
    },
    "createdAt": "..."
  }
}

The caller sends USDC to paymentAddress on the specified chain. The settlement watcher detects the transfer (typical latency 15-30 seconds) and flips the invoice to SETTLED automatically. A polling GET /v1/invoices/{id} is the recommended client UX.

Per-chain notes

Base — `chain: "base"`

The default chain for production agent payments. Coinbase’s L2, deep USDC liquidity, sub-second block times. Use Base for the broadest ecosystem compatibility.

Explorer: basescan.org
Average settlement detection: 15-25 seconds

SKALE Base — `chain: "skale"`

EVM-compatible chain running on the SKALE Network’s Base subnet. Zero gas fees — the chain pre-allocates compute credits, so USDC transfers cost the sender nothing in transaction fees. Best fit for high-frequency agent micropayments where per-tx gas would erode unit economics.

Explorer: skale-base-explorer.skalenodes.com
Chain ID: 1187947933 (0x46CEA59D)
Faucet (testnet): Contact SKALE BD for production credits
Average settlement detection: 15-25 seconds

SKALE Base is the recommended chain for agent-to-agent payments under $1.00 — gasless micropayments without the on-chain fee tail.

Polygon — `chain: "polygon"`

High-throughput EVM L2. Useful for agent flows that originate or terminate in the broader Polygon ecosystem (PoS, ZK-EVM).

Explorer: polygonscan.com
Average settlement detection: 20-40 seconds (slower block times)

Arbitrum One — `chain: "arbitrum"`

Arbitrum’s optimistic rollup. Among the lowest fees of Ethereum L2s for high-frequency micropayments.

Explorer: arbiscan.io
Average settlement detection: 15-25 seconds

Solana — `chain: "solana"`

Native Solana settlement via the PayAI x402 facilitator. SPL Token transfers carry a memo-based invoice reference; settlement detection uses signature polling on the seller wallet.

Explorer: solscan.io
USDC mint: EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v
Token program: TokenkegQfeZyiNwAJbNbGKPFXCWuBvf9Ss623VQ5DA
Average settlement detection: depends on RPC tier (~30 seconds with authed RPC)

Solana detection requires an authenticated RPC endpoint (public mainnet RPC is heavily rate-limited). Set SOLANA_RPC_URL to your Helius / QuickNode / Triton endpoint when self-hosting the settlement watcher.

Settlement flow (all chains)

The lifecycle is identical regardless of chain:

POST /v1/invoices       → invoice created, status=PENDING
<caller transfers USDC> → on the chain specified, to paymentAddress
<watcher detects>       → typically 15-30s after on-chain confirmation
Auto-flip               → status=SETTLED, paymentDetails enriched with
                              txHash + settlementBlockNumber +
                              settlementSource='evm-detector' (or 'solana-detector')
GET /v1/invoices/{id}   → client polls; webhook 'invoice.settled' also fires

The client never needs to PATCH the invoice status. Settlement is a system-detected event.

On-chain audit trail

Every settled invoice produces a DRS receipt anchored on Base (mainnet for production invoices; Base Sepolia for v0.1 PACT Mandate API). The receipt hashes the mandate, settlement details, tax line, and payout breakdown into a single on-chain event that’s verifiable years later via the chain’s explorer. See DRS receipts for the protocol details.

Adding a new chain

We add chains based on real customer pull. Two paths:

EVM chain — if the chain has Coinbase CDP / Polymer / similar x402 facilitator support AND a USDC contract address, integration is typically 2-5 business days.
Non-EVM chain — requires a custom detector module. Solana took ~1 week. Other ecosystems (Aptos, Sui, Tron) would be similar.

To request a chain: email support@invoica.ai with your use case.

Related: x402 Protocol · Invoice Middleware · PACT

Getting Started

Core Concepts

AIAX

Guides

Case Studies

Supported Chains

Supported Chains

All supported chains

How to specify a chain

Per-chain notes

Base — `chain: "base"`

SKALE Base — `chain: "skale"`

Polygon — `chain: "polygon"`

Arbitrum One — `chain: "arbitrum"`

Solana — `chain: "solana"`

Settlement flow (all chains)

On-chain audit trail

Adding a new chain

​Supported Chains

​All supported chains

​How to specify a chain

​Per-chain notes

​Base — chain: "base"

​SKALE Base — chain: "skale"

​Polygon — chain: "polygon"

​Arbitrum One — chain: "arbitrum"

​Solana — chain: "solana"

​Settlement flow (all chains)

​On-chain audit trail

​Adding a new chain

Supported Chains

All supported chains

How to specify a chain

Per-chain notes

Base — `chain: "base"`

SKALE Base — `chain: "skale"`

Polygon — `chain: "polygon"`

Arbitrum One — `chain: "arbitrum"`

Solana — `chain: "solana"`

Settlement flow (all chains)

On-chain audit trail

Adding a new chain