diff --git a/extension/docs/IntegrationGuide.md b/extension/docs/IntegrationGuide.md
index eb23f5e69..dba48af9c 100644
--- a/extension/docs/IntegrationGuide.md
+++ b/extension/docs/IntegrationGuide.md
@@ -102,7 +102,8 @@ or by asynchronous process like [commercetools-payment-to-order-processor job](h
 ### Validate payment
 There must be at least one CTP payment object of type Adyen
 (`Payment.paymentMethodInfo.paymentInterface = ctp-adyen-integration`)
-AND this CTP payment must have `Payment.interfaceId`.
+AND this CTP payment must have `Payment.custom.fields.merchantReference`.
+The combination of `Payment.custom.fields.merchantReference` and `Payment.paymentMethodInfo.paymentInterface` must be unique across the project. This field must not be changed once set.
 
 ### Validate payment transaction
 Cart's payment counts as successful if there is at least one payment object
diff --git a/extension/resources/payment-custom-types.json b/extension/resources/payment-custom-types.json
index 608679ba5..43a4b79f6 100644
--- a/extension/resources/payment-custom-types.json
+++ b/extension/resources/payment-custom-types.json
@@ -7,6 +7,17 @@
     "payment"
   ],
   "fieldDefinitions": [
+    {
+      "type": {
+        "name": "String"
+      },
+      "name": "merchantReference",
+      "label": {
+        "en": "merchantReference"
+      },
+      "required": true,
+      "inputHint": "SingleLine"
+    },
     {
       "type": {
         "name": "String"
diff --git a/extension/src/api/payment/payment.controller.js b/extension/src/api/payment/payment.controller.js
index ce18ac3df..b6b43c3b1 100644
--- a/extension/src/api/payment/payment.controller.js
+++ b/extension/src/api/payment/payment.controller.js
@@ -27,13 +27,13 @@ async function processRequest (request, response) {
   if (adyenValidator.hasErrors())
   // if it's not adyen payment, ignore the payment
     return httpUtils.sendResponse({ response })
-  const interfaceIdValidator = validatorBuilder
-    .validateInterfaceIdField()
-  if (interfaceIdValidator.hasErrors())
+  const merchantReferenceValidator = validatorBuilder
+    .validateMerchantReferenceField()
+  if (merchantReferenceValidator.hasErrors())
     return httpUtils.sendResponse({
       response,
       statusCode: 400,
-      data: interfaceIdValidator.buildCtpErrorResponse()
+      data: merchantReferenceValidator.buildCtpErrorResponse()
     })
   const paymentMethodValidator = validatorBuilder.validatePaymentMethod()
   if (paymentMethodValidator.hasErrors())
diff --git a/extension/src/paymentHandler/cancel-or-refund.handler.js b/extension/src/paymentHandler/cancel-or-refund.handler.js
index 51be608f8..a85706002 100644
--- a/extension/src/paymentHandler/cancel-or-refund.handler.js
+++ b/extension/src/paymentHandler/cancel-or-refund.handler.js
@@ -34,7 +34,7 @@ async function _cancelOrRefundPayment (paymentObject) {
   const body = {
     merchantAccount: config.adyen.merchantAccount,
     originalReference: transaction.interactionId,
-    reference: paymentObject.interfaceId
+    reference: paymentObject.custom.fields.merchantReference
   }
 
   const request = {
diff --git a/extension/src/paymentHandler/creditCard/credit-card-make-payment.handler.js b/extension/src/paymentHandler/creditCard/credit-card-make-payment.handler.js
index d4af0b6c4..8c5149951 100644
--- a/extension/src/paymentHandler/creditCard/credit-card-make-payment.handler.js
+++ b/extension/src/paymentHandler/creditCard/credit-card-make-payment.handler.js
@@ -85,7 +85,7 @@ async function _makePayment (paymentObject) {
       currency: transaction.amount.currencyCode,
       value: transaction.amount.centAmount
     },
-    reference: paymentObject.interfaceId,
+    reference: paymentObject.custom.fields.merchantReference,
     paymentMethod: {
       type: 'scheme',
       encryptedCardNumber: paymentObject.custom.fields.encryptedCardNumber,
diff --git a/extension/src/paymentHandler/kcp/kcp-make-payment.handler.js b/extension/src/paymentHandler/kcp/kcp-make-payment.handler.js
index 9e3823775..c74d9274d 100644
--- a/extension/src/paymentHandler/kcp/kcp-make-payment.handler.js
+++ b/extension/src/paymentHandler/kcp/kcp-make-payment.handler.js
@@ -56,7 +56,7 @@ async function _callAdyen (paymentObject) {
       currency: transaction.amount.currencyCode,
       value: transaction.amount.centAmount
     },
-    reference: paymentObject.interfaceId,
+    reference: paymentObject.custom.fields.merchantReference,
     paymentMethod: {
       type: paymentMethodType
     },
diff --git a/extension/src/paymentHandler/paypal/paypal-make-payment.handler.js b/extension/src/paymentHandler/paypal/paypal-make-payment.handler.js
index 3e9c41779..f4190a19d 100644
--- a/extension/src/paymentHandler/paypal/paypal-make-payment.handler.js
+++ b/extension/src/paymentHandler/paypal/paypal-make-payment.handler.js
@@ -56,7 +56,7 @@ async function _callAdyen (paymentObject) {
       currency: transaction.amount.currencyCode,
       value: transaction.amount.centAmount
     },
-    reference: paymentObject.interfaceId,
+    reference: paymentObject.custom.fields.merchantReference,
     paymentMethod: {
       type: 'paypal'
     },
diff --git a/extension/src/validator/error-messages.js b/extension/src/validator/error-messages.js
index 91cb4b9e8..65fb2c5ad 100644
--- a/extension/src/validator/error-messages.js
+++ b/extension/src/validator/error-messages.js
@@ -9,7 +9,7 @@ module.exports = {
   MISSING_EXPIRY_YEAR: 'Set custom.fields.encryptedExpiryYear',
   MISSING_SECURITY_CODE: 'Set custom.fields.encryptedSecurityCode',
   MISSING_RETURN_URL: 'Set custom.fields.returnUrl',
-  MISSING_INTERFACE_ID: 'Set interfaceId',
+  MISSING_MERCHANT_REFERENCE: 'Set custom merchantReference',
   MISSING_PAYLOAD: 'Set custom.fields.payload',
   MISSING_PAYMENT_DATA: 'Set custom.fields.paymentData',
   MISSING_PARES: 'Set custom.fields.PaRes',
diff --git a/extension/src/validator/validator-builder.js b/extension/src/validator/validator-builder.js
index 6d5c4d383..a761614ff 100644
--- a/extension/src/validator/validator-builder.js
+++ b/extension/src/validator/validator-builder.js
@@ -90,10 +90,10 @@ function withPayment (paymentObject) {
         errors.hasReturnUrl = errorMessages.MISSING_RETURN_URL
       return this
     },
-    validateInterfaceIdField () {
-      const hasInterfaceId = !_.isEmpty(paymentObject.interfaceId)
-      if (!hasInterfaceId)
-        errors.hasInterfaceId = errorMessages.MISSING_INTERFACE_ID
+    validateMerchantReferenceField () {
+      const hasMerchantReference = !_.isEmpty(paymentObject.custom.fields.merchantReference)
+      if (!hasMerchantReference)
+        errors.hasMerchantReference = errorMessages.MISSING_MERCHANT_REFERENCE
       return this
     },
     validatePayloadField () {
diff --git a/extension/test/fixtures/ctp-payment.json b/extension/test/fixtures/ctp-payment.json
index 8ae8790bd..b10c446fb 100644
--- a/extension/test/fixtures/ctp-payment.json
+++ b/extension/test/fixtures/ctp-payment.json
@@ -10,7 +10,6 @@
   "createdBy": {
     "clientId": "GfjD1YgZgpe0K6wEdUEpwTmx"
   },
-  "interfaceId": "paymentReferenceId",
   "amountPlanned": {
     "type": "centPrecision",
     "currencyCode": "EUR",
@@ -27,6 +26,7 @@
       "id": "3bb94fa2-6254-4a31-83e8-a2a882c15173"
     },
     "fields": {
+      "merchantReference": "paymentReferenceId",
       "redirectUrl": "redirectUrl",
       "redirectMethod": "redirectMethod",
       "returnUrl": "returnUrl",
diff --git a/extension/test/fixtures/payment-credit-card-3d.json b/extension/test/fixtures/payment-credit-card-3d.json
index 9e943a001..8434095e5 100644
--- a/extension/test/fixtures/payment-credit-card-3d.json
+++ b/extension/test/fixtures/payment-credit-card-3d.json
@@ -1,5 +1,4 @@
 {
-  "interfaceId":"paymentReferenceId",
   "amountPlanned": {
     "type": "centPrecision",
     "currencyCode": "EUR",
@@ -16,6 +15,7 @@
       "key": "ctp-adyen-integration-payment-custom-type"
     },
     "fields": {
+      "merchantReference": "paymentReferenceId",
       "countryCode": "DE",
       "encryptedCardNumber":"${encryptedCardNumber}",
       "encryptedExpiryMonth":"${encryptedExpiryMonth}",
diff --git a/extension/test/fixtures/payment-credit-card.json b/extension/test/fixtures/payment-credit-card.json
index 0d33e15a3..2b81caf9d 100644
--- a/extension/test/fixtures/payment-credit-card.json
+++ b/extension/test/fixtures/payment-credit-card.json
@@ -1,5 +1,4 @@
 {
-  "interfaceId":"paymentReferenceId",
   "amountPlanned": {
     "type": "centPrecision",
     "currencyCode": "EUR",
@@ -16,6 +15,7 @@
       "key": "ctp-adyen-integration-payment-custom-type"
     },
     "fields": {
+      "merchantReference": "paymentReferenceId",
       "countryCode": "DE",
       "encryptedCardNumber":"${encryptedCardNumber}",
       "encryptedExpiryMonth":"${encryptedExpiryMonth}",
diff --git a/extension/test/fixtures/payment-kcp.json b/extension/test/fixtures/payment-kcp.json
index 692bcf552..1a4838726 100644
--- a/extension/test/fixtures/payment-kcp.json
+++ b/extension/test/fixtures/payment-kcp.json
@@ -1,5 +1,4 @@
 {
-  "interfaceId":"paymentReferenceId",
   "amountPlanned": {
     "type": "centPrecision",
     "currencyCode": "EUR",
@@ -16,6 +15,7 @@
       "key": "ctp-adyen-integration-payment-custom-type"
     },
     "fields": {
+      "merchantReference": "paymentReferenceId",
       "returnUrl":"https://your-company.com/checkout/"
     }
   },
diff --git a/extension/test/fixtures/payment-no-method.json b/extension/test/fixtures/payment-no-method.json
index a7406fbf0..ba607c66a 100644
--- a/extension/test/fixtures/payment-no-method.json
+++ b/extension/test/fixtures/payment-no-method.json
@@ -1,5 +1,4 @@
 {
-  "interfaceId": "pspReference",
   "amountPlanned": {
     "type": "centPrecision",
     "currencyCode": "EUR",
@@ -15,6 +14,7 @@
       "key": "ctp-adyen-integration-payment-custom-type"
     },
     "fields": {
+      "merchantReference": "paymentReferenceId",
       "countryCode": "DE"
     }
   },
diff --git a/extension/test/fixtures/payment-paypal.json b/extension/test/fixtures/payment-paypal.json
index 5a4c68737..64a7926e9 100644
--- a/extension/test/fixtures/payment-paypal.json
+++ b/extension/test/fixtures/payment-paypal.json
@@ -1,5 +1,4 @@
 {
-  "interfaceId":"paymentReferenceId",
   "amountPlanned": {
     "type": "centPrecision",
     "currencyCode": "EUR",
@@ -16,6 +15,7 @@
       "key": "ctp-adyen-integration-payment-custom-type"
     },
     "fields": {
+      "merchantReference":"paymentReferenceId",
       "returnUrl":"https://your-company.com/checkout/"
     }
   },
diff --git a/extension/test/integration/credit-card-make-payment.handler.spec.js b/extension/test/integration/credit-card-make-payment.handler.spec.js
index e61c015b5..4969709c0 100644
--- a/extension/test/integration/credit-card-make-payment.handler.spec.js
+++ b/extension/test/integration/credit-card-make-payment.handler.spec.js
@@ -38,7 +38,7 @@ describe('credit card payment', () => {
 
     const adyenRequestBody = JSON.parse(adyenRequest.body)
     expect(adyenRequestBody.merchantAccount).to.be.equal(process.env.ADYEN_MERCHANT_ACCOUNT)
-    expect(adyenRequestBody.reference).to.be.equal(paymentTemplate.interfaceId)
+    expect(adyenRequestBody.reference).to.be.equal(paymentTemplate.custom.fields.merchantReference)
     expect(adyenRequestBody.returnUrl).to.be.equal(paymentTemplate.custom.fields.returnUrl)
     expect(adyenRequestBody.amount.currency).to.be.equal(paymentTemplate.transactions[0].amount.currencyCode)
     expect(adyenRequestBody.amount.value).to.be.equal(paymentTemplate.transactions[0].amount.centAmount)
@@ -75,7 +75,7 @@ describe('credit card payment', () => {
 
     const adyenRequestBody = JSON.parse(adyenRequest.body)
     expect(adyenRequestBody.merchantAccount).to.be.equal(process.env.ADYEN_MERCHANT_ACCOUNT)
-    expect(adyenRequestBody.reference).to.be.equal(paymentTemplate.interfaceId)
+    expect(adyenRequestBody.reference).to.be.equal(paymentTemplate.custom.fields.merchantReference)
     expect(adyenRequestBody.returnUrl).to.be.equal(`${process.env.API_EXTENSION_BASE_URL}/test-return-url`)
     expect(adyenRequestBody.amount.currency).to.be.equal(paymentTemplate.transactions[0].amount.currencyCode)
     expect(adyenRequestBody.amount.value).to.be.equal(paymentTemplate.transactions[0].amount.centAmount)
diff --git a/extension/test/unit/payment.controller.spec.js b/extension/test/unit/payment.controller.spec.js
index 151bf351b..be4248ea6 100644
--- a/extension/test/unit/payment.controller.spec.js
+++ b/extension/test/unit/payment.controller.spec.js
@@ -26,9 +26,9 @@ describe('Payment controller', () => {
       await paymentController.processRequest(mockRequest)
     })
 
-    it('on missing interface id should throw error', async () => {
+    it('on missing merchant reference should throw error', async () => {
       const ctpPaymentClone = _.cloneDeep(ctpPayment)
-      ctpPaymentClone.interfaceId = ''
+      ctpPaymentClone.custom.fields.merchantReference = ''
 
       utilsStub.collectRequestData = () => JSON.stringify({ resource: { obj: ctpPaymentClone } })
       utilsStub.sendResponse = ({ statusCode, data }) => {
@@ -36,7 +36,7 @@ describe('Payment controller', () => {
         expect(data).to.deep.equal({
           errors: [{
             code: 'InvalidField',
-            message: errorMessages.MISSING_INTERFACE_ID
+            message: errorMessages.MISSING_MERCHANT_REFERENCE
           }]
         })
       }
@@ -46,7 +46,7 @@ describe('Payment controller', () => {
 
     it('on wrong payment method should throw error', async () => {
       const ctpPaymentClone = _.cloneDeep(ctpPayment)
-      ctpPaymentClone.custom.fields = {}
+      ctpPaymentClone.custom.fields = {"merchantReference": "paymentReferenceId"}
       ctpPaymentClone.paymentMethodInfo.method = 'wrong method'
 
       utilsStub.collectRequestData = () => JSON.stringify({ resource: { obj: ctpPaymentClone } })
@@ -65,7 +65,7 @@ describe('Payment controller', () => {
 
     it('on missing params for make paypal payment should throw error', async () => {
       const ctpPaymentClone = _.cloneDeep(ctpPayment)
-      ctpPaymentClone.custom.fields = {}
+      ctpPaymentClone.custom.fields = {"merchantReference": "paymentReferenceId"}
       ctpPaymentClone.paymentMethodInfo.method = 'paypal'
       ctpPaymentClone.transactions[0].state = 'Initial'
 
@@ -85,7 +85,7 @@ describe('Payment controller', () => {
 
     it('on missing params for complete paypal payment should throw error', async () => {
       const ctpPaymentClone = _.cloneDeep(ctpPayment)
-      ctpPaymentClone.custom.fields = {}
+      ctpPaymentClone.custom.fields = {"merchantReference": "paymentReferenceId"}
       ctpPaymentClone.paymentMethodInfo.method = 'paypal'
       ctpPaymentClone.transactions[0].state = 'Pending'
 
@@ -100,7 +100,7 @@ describe('Payment controller', () => {
 
     it('on missing params for make credit card payment should throw error', async () => {
       const ctpPaymentClone = _.cloneDeep(ctpPayment)
-      ctpPaymentClone.custom.fields = {}
+      ctpPaymentClone.custom.fields = {"merchantReference": "paymentReferenceId"}
       ctpPaymentClone.paymentMethodInfo.method = 'creditCard'
       ctpPaymentClone.transactions[0].state = 'Initial'
 
@@ -137,7 +137,7 @@ describe('Payment controller', () => {
 
     it('on missing params for make 3ds payment should throw error', async () => {
       const ctpPaymentClone = _.cloneDeep(ctpPayment)
-      ctpPaymentClone.custom.fields = {}
+      ctpPaymentClone.custom.fields = {"merchantReference": "paymentReferenceId"}
       ctpPaymentClone.paymentMethodInfo.method = 'creditCard_3d'
       ctpPaymentClone.transactions[0].state = 'Initial'
 
@@ -174,7 +174,7 @@ describe('Payment controller', () => {
 
     it('on missing params for complete credit card payment should throw error', async () => {
       const ctpPaymentClone = _.cloneDeep(ctpPayment)
-      ctpPaymentClone.custom.fields = {}
+      ctpPaymentClone.custom.fields = {"merchantReference": "paymentReferenceId"}
       ctpPaymentClone.paymentMethodInfo.method = 'creditCard_3d'
       ctpPaymentClone.transactions[0].state = 'Pending'
 
diff --git a/notification/src/handler/notification/notification.handler.js b/notification/src/handler/notification/notification.handler.js
index 657f2f6ae..2d0295426 100644
--- a/notification/src/handler/notification/notification.handler.js
+++ b/notification/src/handler/notification/notification.handler.js
@@ -37,7 +37,7 @@ async function updatePaymentWithRepeater (payment, notification, ctpClient) {
     try {
       /* eslint-disable-next-line no-await-in-loop */
       await ctpClient.update(ctpClient.builder.payments, currentPayment.id, currentVersion, updateActions)
-      logger.debug(`Payment with interfaceId ${currentPayment.interfaceId}`
+      logger.debug(`Payment with merchantReference ${currentPayment.custom.fields.merchantReference}`
         + 'was successfully updated')
       break
     } catch (err) {
@@ -146,7 +146,7 @@ function getAddTransactionUpdateAction (type, state, amount, currency) {
 
 async function getPaymentByMerchantReference (merchantReference, ctpClient) {
   try {
-    const result = await ctpClient.fetch(ctpClient.builder.payments.where(`interfaceId="${merchantReference}"`))
+    const result = await ctpClient.fetch(ctpClient.builder.payments.where(`custom(fields(merchantReference="${merchantReference}"))`))
     return _.get(result, 'body.results[0]', null)
   } catch (err) {
     throw Error(`Failed to fetch a payment with merchantReference: ${merchantReference}. `
diff --git a/notification/test/integration/init/ensure-payment-custom-type.js b/notification/test/integration/init/ensure-payment-custom-type.js
new file mode 100644
index 000000000..6a782c31f
--- /dev/null
+++ b/notification/test/integration/init/ensure-payment-custom-type.js
@@ -0,0 +1,21 @@
+const paymentCustomType = require('../../resources/payment-custom-types.json')
+
+const utils = require('../../../src/utils/logger')
+
+const logger = utils.getLogger()
+
+async function ensurePaymentCustomType (ctpClient) {
+  try {
+    const { body } = await ctpClient.fetch(ctpClient.builder.types.where(`key="${paymentCustomType.key}"`))
+    if (body.results.length === 0) {
+      await ctpClient.create(ctpClient.builder.types, paymentCustomType)
+      logger.info('Successfully created payment custom type')
+    }
+  } catch (e) {
+    logger.error(e, 'Error when creating payment custom type, skipping...')
+  }
+}
+
+module.exports = {
+  ensurePaymentCustomType
+}
diff --git a/notification/test/integration/init/init-resources.js b/notification/test/integration/init/init-resources.js
index abc32989d..81fd75838 100644
--- a/notification/test/integration/init/init-resources.js
+++ b/notification/test/integration/init/init-resources.js
@@ -1,10 +1,12 @@
 const {
   ensureInterfaceInteractionCustomType
 } = require('../../../src/config/init/ensure-interface-interaction-custom-type')
+const { ensurePaymentCustomType } = require('./ensure-payment-custom-type')
 const { ensurePayment } = require('./ensure-payment')
 
 async function ensureResources (ctpClient) {
   await ensureInterfaceInteractionCustomType(ctpClient)
+  await ensurePaymentCustomType(ctpClient)
   await ensurePayment(ctpClient)
 }
 
diff --git a/notification/test/resources/payment-credit-card.json b/notification/test/resources/payment-credit-card.json
index b3a698863..62e2569c9 100644
--- a/notification/test/resources/payment-credit-card.json
+++ b/notification/test/resources/payment-credit-card.json
@@ -1,7 +1,6 @@
 {
   "id": "123212321",
   "version": "2",
-  "interfaceId":"paymentReferenceId",
   "amountPlanned": {
     "type": "centPrecision",
     "currencyCode": "EUR",
@@ -19,6 +18,7 @@
     },
     "fields": {
       "countryCode": "DE",
+      "merchantReference":"paymentReferenceId",
       "encryptedCardNumber":"${encryptedCardNumber}",
       "encryptedExpiryMonth":"${encryptedExpiryMonth}",
       "encryptedExpiryYear":"${encryptedExpiryYear}",
diff --git a/notification/test/resources/payment-custom-types.json b/notification/test/resources/payment-custom-types.json
index 8e8b7f7e5..f8a3a8f10 100644
--- a/notification/test/resources/payment-custom-types.json
+++ b/notification/test/resources/payment-custom-types.json
@@ -7,6 +7,17 @@
     "payment"
   ],
   "fieldDefinitions": [
+    {
+      "type": {
+        "name": "String"
+      },
+      "name": "merchantReference",
+      "label": {
+        "en": "merchantReference"
+      },
+      "required": true,
+      "inputHint": "SingleLine"
+    },
     {
       "type": {
         "name": "String"
diff --git a/notification/test/resources/payment-draft.json b/notification/test/resources/payment-draft.json
index ee34de69b..76258a066 100644
--- a/notification/test/resources/payment-draft.json
+++ b/notification/test/resources/payment-draft.json
@@ -1,12 +1,19 @@
 {
   "key": "test-payment",
-  "interfaceId": "8313842560770001",
   "amountPlanned": {
     "type": "centPrecision",
     "currencyCode": "EUR",
     "centAmount": 795,
     "fractionDigits": 2
   },
+  "custom": {
+    "type": {
+      "key": "ctp-adyen-integration-payment-custom-type"
+    },
+    "fields": {
+      "merchantReference": "8313842560770001"
+    }
+  },
   "transactions": [
     {
       "type": "Authorization",