Payins API Integration Guide

See core product page here.

Definitions

Term	Definition
Platform	The company that is under contract with zerohash and integrates directly with the zerohash's API
Merchant	A business entity (non-natural person) that serves as the customer-facing front-end in the transaction flow. Typically, the Merchant is a customer of the Platform and is where the Shopper initiates their interaction. In some cases, the Merchant and Platform may be the same entity.
Shopper	The natural person that pays for the good or service

How the Integration Works

A high-level summary of each step of the Payins API integration

Step	Notes
Merchant onboarding	Onboard the merchants that sell goods and services through your platform. Only applicable when Platform is not acting as the Merchant (ex. PSPs that acquire merchants)
Shopper onboarding	Onboard Shoppers making their first crypto or stablecoin purchases
Initiate Shopper's payment	Generate deposit instructions for Shoppers
Initiate refund	Link external account where Shopper will receive funds and facilitate repayment

Payins prerequisites

Complete these checks before you call POST /pay/rfq.

Pre-condition	If missing, `POST /pay/rfq` returns
Ask zerohash to enable this product for you	`401` — `"Your Platform is not configured to use the Pay product"`
Transacting participant has signed the `ACCOUNT_FUNDING_PAY` agreement	`401` — `"Participant has not signed the required agreement for Pay"`
API key has Pay `READ_AND_WRITE` permission	`403` — `"This api key does not have write permission to this endpoint"` (`GET` endpoints return the read-permission variant)

1. Submit Merchant

ℹ️
Who this applies to
This guide is relevant when the Platform has many merchants. If the Platform is itself the merchant, this step is not required.

Begin by submitting the Merchant via POST /participants/entity/new. See more information here.

2. Query Merchant

You can query already-submitted Merchants via the GET /participants endpoint. If you'd like to query a specific Merchant, use theparticipant_code parameter.

3. Fund Refund Account

To enable future refunds, you must pre-fund your Refund account by sending a wire transfer to the designated bank account provided by our settlement team. Ensure the wire memo is tagged with your Platform code + "_refund" (ie, PLAT01_refund):

Here are the account details:

Participant_code: 00SCXM
Account_group: PLAT01 (replace with your participant_code)
Account_label: pay_refund
Account_type: available
Asset: USD

4. Submit Shopper

Next, you'll need to onboard the end users (ie, "Shoppers"). Depending on transaction type and the Shopper's transaction volume and residence, we have differing level of diligence requirements. See more information on Shopper Onboarding here.

Use POST /participants/customers/new to create a new Shopper. Set the onboarding_profile attribute to shopper to distinguish this participant from a standard participant.

Sample Request

{
  "onboarding_profile": "shopper",
  "email": "[email protected]"
}

Shoppers with onboarding_profile = shopper are auto-approved upon creation as long as the minimum required data is present: a phone_number or email. No additional fields are required at creation time. Further data can be added later via PATCH or invocation of the Payins SDK as the shopper's transaction tier requires it.

📘
Signature Collection
For the Payins API Solution, it is critical that you collect consent from the Shopper to zerohash's user agreements and share confirmation that consent was collected through the POST /participants/customers/new endpoint.

5. Query Shopper

To retrieve general information about the Shopper, query the GET /participants endpoint. You can use the participant_code filter to retrieve an individual Shopper.

6. Query Shopper Limits

To retrieve transaction limits for a Shopper's tier, query the GET /pay/limits endpoint. You can use the participant_code filter to retrieve an individual Shopper.

Example Response:

{
  "message": {
    "request_id": "test-request-id",
    "participant_code": "SHOPP1",
    "merchant_participant_code": "MERCH1",
    "merchant_classification": "NON-TRANSFERABLE-3",
    "current_level": 2,
    "current_limits": [
      {
        "limit": "1000.00",
        "spent": "250.00",
        "remaining": "750.00",
        "window": "daily"
      }
    ],
    "platform_totals": [
      {
        "window": "daily",
        "currency": "USD",
        "total_amount": "5000.00",
        "transaction_count": 12
      }
    ],
    "merchant_totals": [
      {
        "window": "daily",
        "currency": "USD",
        "total_amount": "250.00",
        "transaction_count": 3
      }
    ]
  }
}

7. Accounts

The Platform will have the following accounts at zerohash:

Account	Description	Technical Details
Settlement Account	The fiat account that contains the balance of successful payments	- `participant_code` = [your platform code or merchant's participant code] - `account_group` = [your platform code] - `account_label` = pay - `account_type` = available - `asset` = USD (or other fiat currency being used)
Refund Float Account	The fiat account, funded by the Platform, that is used to refund Shoppers. The balances here will be converted to a crypto or stablecoin asset and sent on-chain to the Shopper. See section, "11. Refund a Payment" below for details	- `participant_code` = 00SCXM - `account_group` = [your platform code] - `account_label` = pay_refund - `account_type` = available - `asset` = USD (or other fiat currency being used)
Error Account	The fiat account that accumulates due to error scenarios (over payment, under payment, incorrect asset or network, late payment	- `participant_code` = [your platform code or merchant's participant code] - `account_group` = [your platform code] - `account_label` = pay_error - `account_type` = available - `asset` = USD (or other fiat currency being used)

8. Initiate Payment

Request a quote - POST /pay/rfq

Generate quote for the payment amount.

Example Request:

{
  "participant_code": "SHOPP1",
  "pay_asset": "USDC",
  "quoted_total": "100.00",
  "quoted_currency": "USD",
  "account_label": "pay",
  "client_reference_id": "order-12345",
  "merchant_participant_code": "MERCH01" //optional, only use when Platform!= Merchant
}

Interpretation of this request - the Shopper (SHOPP1) is making a $100 payment to the Merchant (MERCH01)using USDC as the payment asset. quoted_currency is an enum with one supported value: USD.

Example Response:

{
  "request_id": "14f8ebb8-7530-4aa4-bef9-9d73d56313f3",
  "participant_code": "SHOPP1",
  "pay_asset": "USDC",
  "rate": "1",
  "quoted_currency": "USD",
  "quoted_total": "100",
  "underlying_quantity": "100",
  "price_expire_ts": null,
  "deposit_address": "0x5f59B625036ccB4f7aD27Ca4Cb896e4452AfFDAF",
  "transaction_id": "550e8400-e29b-41d4-a716-446655440000",
  "client_reference_id": "order-1001",
  "is_static": true
}

Field	Type	Notes
`request_id`	UUID string	Echoed back from Zero Hash for request correlation.
`participant_code`	string	Shopper participant code.
`pay_asset`	string	Network-qualified asset, such as `USDC.SOL`, `USDC.BASE`, or `BTC`.
`rate`	decimal string	Quoted rate at the moment of RFQ.
`quoted_currency`	string	Enum: `USD`.
`quoted_total`	decimal string	Amount in `quoted_currency`.
`underlying_quantity`	decimal string	Amount in `pay_asset`.
`price_expire_ts`	ISO 8601 UTC string or `null`	May be `null` for stablecoins.
`deposit_address`	string	Blockchain address on the `pay_asset` network.
`transaction_id`	UUID string	Use this as the path parameter for `POST /pay/{id}/rfq`. This is distinct from the settled `transaction_id` in webhook payloads and `GET /pay/transactions` rows.
`client_reference_id`	string, optional	Whatever you sent on the request, echoed back. This is a free-form string.
`is_static`	boolean	Indicates whether the deposit address is reused or generated per RFQ

End customer initiates on-chain payment

On the Platform's user interface, the Shopper is presented with the deposit_address returned by POST /pay/rfq, and the amount to deposit. They use their Metamask wallet, for example, to trigger a withdrawal into the deposit_address for the amount of the payment.

Payment Successful

Successful Payment (exact amount)

Once a successful payment is received for the exact amount, we'll send a webhook to you that looks like this:

{
  "participant_code": "SHOPP1",
  "fund_asset": "USDC.BASE",
  "rate": "1",
  "quoted_currency": "USD",
  "source_address": "external",
  "deposit_address": "0xb07C48f0BF25A97034c818Dc643A98e42703D20c",
  "quantity": "100",
  "notional": "100",
  "fund_id": "6767a149-4771-4166-ba07-a2542e361318",
  "fund_timestamp": 1756376889792000000,
  "deposit_timestamp": 1756376889499000000,
  "transaction_id": "d1d731ed-952c-410e-b62b-eb00e3d096fc",
  "account_label": "general",
  "success": true,
  "status_reason_code": "DEPOSIT_PROCESSED",
  "reference_id": "04918aef-41d1-4dfb-82b8-2fdc232a8d88",
  "raw_fee_bps": "",
  "deposit_fee_bps": "",
  "raw_fee_notional": "",
  "deposit_fee_notional": ""
}

Successful Payment (over payment)

Once a successful payment is received where the Shopper sent too much, we'll send a webhook to you that looks like this:

{
  "participant_code": "SHOPP1",
  "fund_asset": "USDC.BASE",
  "rate": "1",
  "quoted_currency": "USD",
  "source_address": "external",
  "deposit_address": "0xb07C48f0BF25A97034c818Dc643A98e42703D20c",
  "quantity": "100",
  "notional": "100",
  "fund_id": "6767a149-4771-4166-ba07-a2542e361318",
  "fund_timestamp": 1756376889792000000,
  "deposit_timestamp": 1756376889499000000,
  "transaction_id": "d1d731ed-952c-410e-b62b-eb00e3d096fc",
  "account_label": "general",
  "success": true,
  "status_reason_code": "DEPOSIT_PROCESSED",
  "status_reason": "over payment",
  "reference_id": "04918aef-41d1-4dfb-82b8-2fdc232a8d88",
  "raw_fee_bps": "",
  "deposit_fee_bps": "",
  "raw_fee_notional": "",
  "deposit_fee_notional": ""
}

Payment Unsuccessful

Failure scenario	Expected remediation steps
Under payment	Shopper to contact Platform → Platform to facilitate a withdraw via `POST /payments` to Shopper's wallet
Depeg	Shopper to contact Platform → Platform to contact zerohash via Slack or Email to facilitate withdrawals back to the Shopper manually
Above max threshold	Shopper to contact Platform → Platform to contact zerohash via Slack or Email to facilitate withdrawals back to the Shopper manually
Quarantine	Shopper to contact Platform → Platform to contact zerohash via Slack or Email. Note: zerohash will likely `disable` this Shopper, as this scenario is typically triggered due receiving a deposit from a high-risk source address
Late payment	Shopper to contact Platform → Platform to facilitate a withdraw via `POST /payments` to Shopper's wallet
Wrong asset or network	Shopper to contact Platform → Platform to facilitate a withdraw via `POST /payments` to Shopper's wallet

Payment Unsuccessful (under payment)

Upon a payment for an insufficient amount, a webhook notification will be triggered as follows

{
  "participant_code": "SHOPP1",
  "fund_asset": "USDC.BASE",
  "rate": "1",
  "quoted_currency": "USD",
  "source_address": "external",
  "deposit_address": "0xb07C48f0BF25A97034c818Dc643A98e42703D20c",
  "quantity": "90",
  "notional": "",
  "fund_id": "6767a149-4771-4166-ba07-a2542e361318",
  "fund_timestamp": 1756376889792000000,
  "deposit_timestamp": 1756376889499000000,
  "transaction_id": "d1d731ed-952c-410e-b62b-eb00e3d096fc",
  "account_label": "general",
  "success": false,
  "status_reason_code": "PROCESSING_FAILED",
  "status_reason": "under payment",
  "reference_id": "04918aef-41d1-4dfb-82b8-2fdc232a8d88",
  "raw_fee_bps": "",
  "deposit_fee_bps": "",
  "raw_fee_notional": "",
  "deposit_fee_notional": ""
}

Successful Payment (depeg)

If a stablecoin becomes depegged, to mitigate zerohahs's risk, we will manually mark the asset as depegged on our side. This will block all “sell” transactions converting that stablecoin to USD. Should we receive a payment deposit during this period, we will not convert the deposit to fiat. Instead, the funds will be moved to a dedicated depeg account, and a webhook notification will be triggered as follows:

{
  "participant_code": "SHOPP1",
  "fund_asset": "USDC.BASE",
  "rate": "1",
  "quoted_currency": "USD",
  "source_address": "external",
  "deposit_address": "0xb07C48f0BF25A97034c818Dc643A98e42703D20c",
  "quantity": "100",
  "notional": "",
  "fund_id": "6767a149-4771-4166-ba07-a2542e361318",
  "fund_timestamp": 1756376889792000000,
  "deposit_timestamp": 1756376889499000000,
  "transaction_id": "d1d731ed-952c-410e-b62b-eb00e3d096fc",
  "account_label": "general",
  "success": false,
  "status_reason_code": "PROCESSING_FAILED",
  "status_reason": "depeg",
  "reference_id": "04918aef-41d1-4dfb-82b8-2fdc232a8d88",
  "raw_fee_bps": "",
  "deposit_fee_bps": "",
  "raw_fee_notional": "",
  "deposit_fee_notional": ""
}

Above max threshold

zerohash has certain liquidation maximums on our end. If a large deposit is received above this threshold, a webhook notification will be triggered as follows:

{
  "participant_code": "SHOPP1",
  "fund_asset": "USDC.BASE",
  "rate": "1",
  "quoted_currency": "USD",
  "source_address": "external",
  "deposit_address": "0xb07C48f0BF25A97034c818Dc643A98e42703D20c",
  "quantity": "10000000",
  "notional": "",
  "fund_id": "6767a149-4771-4166-ba07-a2542e361318",
  "fund_timestamp": 1756376889792000000,
  "deposit_timestamp": 1756376889499000000,
  "transaction_id": "d1d731ed-952c-410e-b62b-eb00e3d096fc",
  "account_label": "general",
  "success": false,
  "status_reason_code": "PROCESSING_FAILED",
  "status_reason": "above max threshold",
  "reference_id": "04918aef-41d1-4dfb-82b8-2fdc232a8d88",
  "raw_fee_bps": "",
  "deposit_fee_bps": "",
  "raw_fee_notional": "",
  "deposit_fee_notional": ""
}

Quarantine

If zerohash detects that the source address of the payment deposit is high-risk, a webhook notification will be triggered as follows:

{
  "participant_code": "SHOPP1",
  "fund_asset": "USDC.BASE",
  "rate": "1",
  "quoted_currency": "USD",
  "source_address": "external",
  "deposit_address": "0xb07C48f0BF25A97034c818Dc643A98e42703D20c",
  "quantity": "10000000",
  "notional": "",
  "fund_id": "6767a149-4771-4166-ba07-a2542e361318",
  "fund_timestamp": 1756376889792000000,
  "deposit_timestamp": 1756376889499000000,
  "transaction_id": "d1d731ed-952c-410e-b62b-eb00e3d096fc",
  "account_label": "general",
  "success": false,
  "status_reason_code": "PROCESSING_FAILED",
  "status_reason": "For Zero Hash Compliance reasons, the deposit has not been converted to fiat and the crypto has been credited to a Zero Hash holding account",
  "reference_id": "04918aef-41d1-4dfb-82b8-2fdc232a8d88",
  "raw_fee_bps": "",
  "deposit_fee_bps": "",
  "raw_fee_notional": "",
  "deposit_fee_notional": ""
}

Late payment

If zerohash receives a payment deposit past the Payment Window, a webhook notification will be triggered as follows:

{
  "participant_code": "SHOPP1",
  "fund_asset": "USDC.BASE",
  "rate": "1",
  "quoted_currency": "USD",
  "source_address": "external",
  "deposit_address": "0xb07C48f0BF25A97034c818Dc643A98e42703D20c",
  "quantity": "10000000",
  "notional": "",
  "fund_id": "6767a149-4771-4166-ba07-a2542e361318",
  "fund_timestamp": 1756376889792000000,
  "deposit_timestamp": 1756376889499000000,
  "transaction_id": "d1d731ed-952c-410e-b62b-eb00e3d096fc",
  "account_label": "general",
  "success": false,
  "status_reason_code": "DEPOSIT_WINDOW_EXPIRED",
  "status_reason": "payment session has expired",
  "reference_id": "04918aef-41d1-4dfb-82b8-2fdc232a8d88",
  "raw_fee_bps": "",
  "deposit_fee_bps": "",
  "raw_fee_notional": "",
  "deposit_fee_notional": ""
}

Wrong asset or network

If zerohash receives a payment deposit for an asset that was not selected by the Shopper on the Select Asset page, a webhook notification will be triggered as follows:

{
  "participant_code": "SHOPP1",
  "fund_asset": "ETH",
  "rate": "1",
  "quoted_currency": "USD",
  "source_address": "external",
  "deposit_address": "0xb07C48f0BF25A97034c818Dc643A98e42703D20c",
  "quantity": ".15",
  "notional": "",
  "fund_id": "6767a149-4771-4166-ba07-a2542e361318",
  "fund_timestamp": 1756376889792000000,
  "deposit_timestamp": 1756376889499000000,
  "transaction_id": "d1d731ed-952c-410e-b62b-eb00e3d096fc",
  "account_label": "general",
  "success": false,
  "status_reason_code": "PROCESSING_FAILED",
  "status_reason": "deposit currency does not match the expected currency",
  "reference_id": "04918aef-41d1-4dfb-82b8-2fdc232a8d88",
  "raw_fee_bps": "",
  "deposit_fee_bps": "",
  "raw_fee_notional": "",
  "deposit_fee_notional": ""
}

9. Query payments

You can query our REST endpoint GET /pay/transactions to retroactively view payment details.

Query parameters

All filters combine with AND. The response shape matches the List payin transactions reference page.

Query param	Type	Notes
`participant_code`	string	Required for default listing.
`page`	integer	Default `1`.
`page_size`	integer	Default `50`, capped at `50`. Passing `100` is silently clamped.
`transaction_id`	string	Exact match on the settled transaction ID.
`pay_asset`	string	Asset filter, such as `USDC.SOL`. Response rows return this value as `fund_asset`.
`success`	boolean	`true` returns only settled-with-success transactions.
`client_reference_id`	string	Exact match on the value you sent in the RFQ.
`deposit_timestamp_gte`	integer, Unix seconds	Lower-bound inclusive.
`deposit_timestamp_gt`	integer, Unix seconds	Lower-bound exclusive.
`deposit_timestamp_lte`	integer, Unix seconds	Upper-bound inclusive.
`deposit_timestamp_lt`	integer, Unix seconds	Upper-bound exclusive.

Sample Response:

    {
      "participant_code": "SHOPP1",
      "fund_asset": "USDC",
      "quoted_currency": "USD",
      "deposit_address": "0xabc123usdcwalletaddress",
      "rate": "1.00",
      "quantity": "100.00",
      "notional": "100.00",
      "fund_timestamp": 1712756400,
      "transaction_id": "111e8400-e29b-41d4-a716-446655440000",
      "account_label": "pay",
      "fund_id": "fund-usdc-1001",
      "success": true,
      "status_reason": "",
      "status_reason_code": "",
      "is_first_deposit": true,
      "raw_fee_bps": "25",
      "actual_fee_bps": "25",
      "raw_fee_notional": "0.25",
      "actual_fee_notional": "0.25",
      "deposit_timestamp": 1712756700,
      "source_address": "0xsenderwallet123",
      "deposited_asset": "USDC",
      "client_reference_id": "order-1001",
      "source": {
        "source_type": "on_chain",
        "integration": "ethereum"
      },
      "deposit_fee_type": "DEPOSIT_FEE_TYPE_FLAT",
      "fee_tier_breakdown": []
    }
  ],
  "page": 1,
  "page_size": 50,
  "total_pages": 1
}

10. Settlement

Withdrawals from Merchant or Platform participant accounts to external bank accounts can be initiated through POST /withdrawals/requests.

11. Refund a Payment

In order to initiate a refund, you should use the following endpoints:

POST /payments/external_accounts - links a crypto account where the Shopper will receive their refund
POST /payments - initiates a conversion from USD (using Refund account) to the crypto asset. This API call will also automatically and immediately send the funds on-chain.

🚧
IMPORTANT: You cannot rely on the deposit’s source address as the refund destination. Blockchain transactions are not inherently bidirectional, and returning funds to the sender address may result in loss of funds or failed deliveries.
Some Platforms may choose to pair their zerohash integration with their own transaction monitoring tools. In situations where zerohash accepts a deposit, but the Platform’s monitoring logic flags and rejects it, the Platform may opt to return the deposit by using the POST /convert_withdraw/rfq and POST /convert_withdraw/execute endpoint.
The required flow is to always request and confirm a return address directly from the Shopper before initiating the return.
Please speak to a zerohash solutions engineer for guidance if interested in this flow.

Definitions

How the Integration Works

Payins prerequisites

1. Submit Merchant

Who this applies to

2. Query Merchant

3. Fund Refund Account

4. Submit Shopper

Signature Collection

5. Query Shopper

6. Query Shopper Limits

7. Accounts

8. Initiate Payment

Request a quote - POST /pay/rfq

End customer initiates on-chain payment

Payment Successful

Successful Payment (exact amount)

Successful Payment (over payment)

Payment Unsuccessful

Payment Unsuccessful (under payment)

Successful Payment (depeg)

Above max threshold

Quarantine

Late payment

Wrong asset or network

9. Query payments

Query parameters

10. Settlement

11. Refund a Payment

IMPORTANT: You cannot rely on the deposit’s source address as the refund destination. Blockchain transactions are not inherently bidirectional, and returning funds to the sender address may result in loss of funds or failed deliveries.