---
url: /docs/kb.md
description: >-
  Reference guides for supported chains, countries, payment methods, compliance
  requirements, and processing timelines.
---

Reference guides for topics that span the API: chains and tokens, compliance, and processing timelines.

## Guides

| Guide | What it covers |
| --- | --- |
| [Supported chains](/kb/supported-chains) | Chain and token matrix across payins, payouts, wallets, and transfers |
| [Smart contracts](/kb/smart-contracts) | USDB test stablecoin and its contract addresses across supported networks |
| [Cut-off times](/kb/cut-off-times) | Processing windows for ACH, wire, SWIFT, Pix, SPEI, and more |
| [Supported countries](/kb/supported-countries) | Every country by tier: standard, high-risk, and prohibited |
| [Payment methods](/kb/payment-methods) | Bank rails by country and currency, for payins and payouts |
| [Prohibited activities](/kb/prohibited-activities) | High-risk and prohibited business activities, and disclosure obligations |
| [Payout descriptor](/kb/payout-descriptor) | How the sender's name appears on a recipient's bank statement, per rail |
| [KYC requirements](/kb/kyc) | Verification levels, required fields, limits, and the terms of service flow |
| [KYC basics](/kb/kyc-basics) | Document-quality standards and submission guidelines for individuals |
| [On-hold transactions](/kb/on-hold-transactions) | Transactions held for compliance review and how they resolve |
| [SWIFT deliverability](/kb/swift-deliverability) | Documents and address formatting that maximize SWIFT delivery success |
| [SWIFT statuses](/kb/swift-statuses) | Tracking SWIFT compliance documents through review and approval |
| [KYB documents](/kb/kyb-documents) | Business verification documents: formation, ownership, UBOs, and address |
| [Proof of address](/kb/proof-of-address) | Accepted proof-of-address documents for businesses and individuals |
| [Source of funds](/kb/source-of-funds) | Documentation to verify source of funds and source of wealth |
| [NAICS codes](/kb/naics-codes) | Find the NAICS industry code for your business during onboarding |
| [Nested payments](/kb/nested-payments) | Recognizing payments made on behalf of unseen parties, and staying compliant |
| [Information requests](/kb/information-requests) | How RFIs work when compliance needs missing KYC or KYB details |
| [Virtual accounts](/kb/virtual-accounts) | Documentation for the virtual account evaluation, beyond standard KYB |
| [Rejection reasons](/kb/rejection-reasons) | Reason codes returned when an application or document is rejected |