question

This is a bit complicated, so I've included an image of a compliant receipt and the JSON that would be expected from the payment object. I'll list the required fields and some comments for each.

1. Tender/sale type (payment.tender): should be able to use tender.label as shown in JSON below. Should be usually "DEBIT CARD" or "CREDIT CARD"; your app will need to determine how to handle tender types that are not one of those two.
2. payment.cardTransaction.type: Confusingly this will typically come back as 'PREAUTH' or 'AUTH', but the receipt should say 'AUTH' or 'SALE' for those results, respectively.
3. payment.clientCreatedTime: The receipt of course, must display the time of transaction somewhere
4. Amount (payment.amount): Should be obvious
5. Method (payment.cardTransaction.entryType): See image below for translation from "EMV_CONTACT" to "EMV" for example.
6. Card label, should be either in payment.cardTransaction.applicationLabel for EMV and most NFC transactions, or should use the tender type (credit card or debit card) as mentioned above. Unfortunately, the applicationLabel is stored as a hex string of the bytes that can be converted into an ASCII string. You can decode the hex characters into bytes and then render those as a string in code, or if on a Unix machine, you can do the same by running "echo '5649534120435245444954' | xxd -revert -p", which would return "VISA CREDIT" in the below example.
7. Reference number (payment.cardTransaction.referenceId): Usually used for chargebacks
8. Authorization code (payment.cardTransaction.authCode): Definitely required
9. MID: This is obtainable via the web services via "/v3/merchants/{merchantId}?expand=gateway" call (I've shown an example below).
10. AID: (payment.cardTransaction.extra.applicationIdentifier): Application identifier (EMV only)
11. Cardholder verification method (aka CVM) - (payment.cardTransaction.extra.cvmResult)

nocardholderverification --- NO CARDHOLDER VERIFICATION

pin_verified --- PIN VERIFIED

device_verified --- DEVICE VERIFIED

signature_verified --- SIGNATURE VERIFIED

pinandsignature_verified --- PIN & SIGNATURE VERIFIED

Payment object JSON example: {baseUrl}/v3/merchants/{mId}/payments/{pId}?expand=cardTransaction,tender

{
    "amount": 39,
    "cardTransaction": {
        "authCode": "032973",
        "cardType": "VISA",
        "entryType": "EMV_CONTACT",
        "extra": {
            "applicationIdentifier": "A0000000031010",
            "applicationLabel": "5649534120435245444954", /** ("VISA CREDIT") **/
            "card": "{\"SourceReasonCode\":\"3\",\"CardLevelResult\":\"A \",\"ACI\":\"E\",\"TransID\":\"305351679480093FRGX\"}",
            "common": "{\"LocalDateTime\":\"20151217185226\",\"POSEntryMode\":\"051\",\"POSID\":\"0217\",\"MerchID\":\"RCTST0000008099\",\"TermEntryCapablt\":\"04\",\"STAN\":\"000238\",\"POSCondCode\":\"00\",\"TermID\":\"00000001\",\"TrnmsnDateTime\":\"20151217185226\"}",
            "cvmResult": "SIGNATURE",
            "func": "CREDIT",
            "iccContainer": "82025C005F3401019F02060000000000399F03060000000000005F2A0208409F0702FF009F0D05F0400088009F0E0500100000009F0F05F040009800500B56495341204352454449549F2608D4C76E51FFF28C839F0607A00000000310109F3602002F9F0902008C9F2701809F34031E03009F100706010A03A000009F3901059F3303E0F8C89F1A0208409F3501229505020000C0009A031512179B02E8009C01009F3704B77EA08B9F21031052278407A0000000031010"
        },
        "last4": "0010",
        "paymentRef": {
            "id": "05NAGREFN0K9C"
        },
        "referenceId": "535100000238",
        "state": "PENDING",
        "transactionNo": "000012", /** optional **/
        "type": "PREAUTH"
    },
    "cashbackAmount": 0,
    "clientCreatedTime": 1450378346000, /** 17 Dec 2015 10:49:44 AM **/
    "createdTime": 1450378347000,
    "device": {
        "id": "1d57378e-549c-4176-11d8-a2cb7a514ef9"
    },
    "employee": {
        "id": "ERDY7VA92Y3MP"
    },
    "id": "05NAGREFN0K9C",
    "modifiedTime": 1450378348000,
    "offline": false,
    "order": {
        "id": "XHBWZG3RNGJ2J"
    },
    "result": "SUCCESS",
    "taxAmount": 0,
    "tender": {
        "editable": false,
        "enabled": true,
        "href": "http://192.168.1.100:9001/v3/merchants/KWMJ1P0WCPBW4/tenders/J3S838WQESYAA",
        "id": "J3S838WQESYAA",
        "label": "Credit Card",
        "labelKey": "com.clover.tender.credit_card",
        "opensCashDrawer": false,
        "visible": true
    }
}

"/v3/merchants/{merchantId}?expand=gateway" example:

{
    "address": {
        "href": "http://192.168.1.100:9001/v3/merchants/KWMJ1P0WCPBW4/address"
    },
    "createdTime": 1448058800000,
    "gateway": {
        "accountName": "USA MOORE CONSULTING",
        "authorizationFrontEnd": "Nashville",
        "backendMid": "RCTST0000008099",
        "frontendMid": "RCTST0000008099",
        "mid": "RCTST0000008099",
        "newBatchCloseEnabled": true,
        "paymentGatewayApi": "FDCRCIP",
        "supportsNakedCredit": true,
        "supportsTipAdjust": true,
        "supportsTipping": true,
        "tid": "00000001"
    },
    "href": "http://192.168.1.100:9001/v3/merchants/KWMJ1P0WCPBW4",
    "id": "KWMJ1P0WCPBW4",
    "isBillable": true,
    "merchantPlan": {
        "id": "Q94B0SXGP7JJ6"
    },
    "modifierGroups": {
        "href": "http://192.168.1.100:9001/v3/merchants/KWMJ1P0WCPBW4/modifier_groups"
    },
    "name": "USA MOORE CONSULTING",
...
}