diff --git a/TransactionProcessor.BusinessLogic.Tests/Services/MerchantDomainServiceTests.cs b/TransactionProcessor.BusinessLogic.Tests/Services/MerchantDomainServiceTests.cs
index 4c2914a7..ee303f23 100644
--- a/TransactionProcessor.BusinessLogic.Tests/Services/MerchantDomainServiceTests.cs
+++ b/TransactionProcessor.BusinessLogic.Tests/Services/MerchantDomainServiceTests.cs
@@ -130,6 +130,8 @@ public async Task MerchantDomainService_CreateMerchant_EstateNotFound_ErrorThrow
     public async Task MerchantDomainService_AssignOperatorToMerchant_OperatorAssigned() {
         this.AggregateService.Setup(m => m.GetLatest<MerchantAggregate>(It.IsAny<Guid>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(Result.Success(TestData.Aggregates.CreatedMerchantAggregate()));
+        this.AggregateService.Setup(m => m.GetLatest<OperatorAggregate>(It.IsAny<Guid>(), It.IsAny<CancellationToken>()))
+            .ReturnsAsync(Result.Success(TestData.Aggregates.CreatedOperatorAggregate()));
         this.AggregateService
             .Setup(m => m.Save(It.IsAny<MerchantAggregate>(), It.IsAny<CancellationToken>()))
             .ReturnsAsync(Result.Success);
diff --git a/TransactionProcessor.BusinessLogic/Services/MerchantDomainService.cs b/TransactionProcessor.BusinessLogic/Services/MerchantDomainService.cs
index 82240115..facccb11 100644
--- a/TransactionProcessor.BusinessLogic/Services/MerchantDomainService.cs
+++ b/TransactionProcessor.BusinessLogic/Services/MerchantDomainService.cs
@@ -114,7 +114,7 @@ public async Task<Result> AssignOperatorToMerchant(MerchantCommands.AssignOperat
                     return ResultHelpers.CreateFailure(estateResult);
 
                 Result<MerchantAggregate> merchantResult = await DomainServiceHelper.GetAggregateOrFailure(ct => this.AggregateService.GetLatest<MerchantAggregate>(command.MerchantId, ct), command.MerchantId, cancellationToken);
-                if (estateResult.IsFailed)
+                if (merchantResult.IsFailed)
                     return ResultHelpers.CreateFailure(merchantResult);
 
                 EstateAggregate estateAggregate = estateResult.Data;
@@ -131,25 +131,26 @@ public async Task<Result> AssignOperatorToMerchant(MerchantCommands.AssignOperat
                     return Result.Invalid($"Operator Id {command.RequestDto.OperatorId} is not supported on Estate [{estate.Name}]");
                 }
 
-                // TODO: Reintroduce when we have an Operator Aggregate
-                // https://github.com/TransactionProcessing/EstateManagement/issues/558
+                Result<OperatorAggregate> operatorResult = await DomainServiceHelper.GetAggregateOrFailure(ct => this.AggregateService.GetLatest<OperatorAggregate>(command.RequestDto.OperatorId, ct), command.RequestDto.OperatorId, cancellationToken);
+                if (operatorResult.IsFailed)
+                    return ResultHelpers.CreateFailure(operatorResult);
+                OperatorAggregate @operatorAggregate = operatorResult.Data;
                 // Operator has been validated, now check the rules of the operator against the passed in data
-                //if (@operator.RequireCustomMerchantNumber) {
-                //    // requested addition must have a merchant number supplied
-                //    if (String.IsNullOrEmpty(command.RequestDto.MerchantNumber)) {
-                //        throw new InvalidOperationException($"Operator Id {command.RequestDto.OperatorId} requires that a merchant number is provided");
-                //    }
-                //}
-
-                //if (@operator.RequireCustomTerminalNumber) {
-                //    // requested addition must have a terminal number supplied
-                //    if (String.IsNullOrEmpty(command.RequestDto.TerminalNumber)) {
-                //        throw new InvalidOperationException($"Operator Id {command.RequestDto.OperatorId} requires that a terminal number is provided");
-                //    }
-                //}
+                if (@operatorAggregate.RequireCustomMerchantNumber) {
+                    // requested addition must have a merchant number supplied
+                    if (String.IsNullOrEmpty(command.RequestDto.MerchantNumber)) {
+                        return Result.Invalid($"Operator Id {command.RequestDto.OperatorId} requires that a merchant number is provided");
+                    }
+                }
+
+                if (@operatorAggregate.RequireCustomTerminalNumber) {
+                    // requested addition must have a terminal number supplied
+                    if (String.IsNullOrEmpty(command.RequestDto.TerminalNumber)) {
+                        return Result.Invalid($"Operator Id {command.RequestDto.OperatorId} requires that a terminal number is provided");
+                    }
+                }
 
                 // Assign the operator
-                // TODO: Swap second parameter to name
                 Result stateResult = merchantAggregate.AssignOperator(command.RequestDto.OperatorId, @operator.Name, command.RequestDto.MerchantNumber, command.RequestDto.TerminalNumber);
                 if (stateResult.IsFailed)
                     return stateResult;
diff --git a/TransactionProcessor.IntegrationTests/Features/Contract.feature b/TransactionProcessor.IntegrationTests/Features/Contract.feature
index 03fd9f55..a59c4014 100644
--- a/TransactionProcessor.IntegrationTests/Features/Contract.feature
+++ b/TransactionProcessor.IntegrationTests/Features/Contract.feature
@@ -30,8 +30,8 @@ Background:
 	
 	Given I have created the following operators
 	| EstateName    | OperatorName    | RequireCustomMerchantNumber | RequireCustomTerminalNumber |
-	| Test Estate 1 | Test Operator 1 | True                        | True                        |
-	| Test Estate 2 | Test Operator 1 | True                        | True                        |
+	| Test Estate 1 | Test Operator 1 | False                        | False                        |
+	| Test Estate 2 | Test Operator 1 | False                        | False                        |
 
 	And I have assigned the following operators to the estates
 	| EstateName    | OperatorName    | 
diff --git a/TransactionProcessor.IntegrationTests/Features/LogonTransaction.feature b/TransactionProcessor.IntegrationTests/Features/LogonTransaction.feature
index bd47372d..aec2c1f7 100644
--- a/TransactionProcessor.IntegrationTests/Features/LogonTransaction.feature
+++ b/TransactionProcessor.IntegrationTests/Features/LogonTransaction.feature
@@ -27,7 +27,7 @@ Background:
 
 	Given I have created the following operators
 	| EstateName    | OperatorName    | RequireCustomMerchantNumber | RequireCustomTerminalNumber |
-	| Test Estate 1 | Test Operator 1 | True                        | True                        |
+	| Test Estate 1 | Test Operator 1 | False                        | False                        |
 
 	And I have assigned the following operators to the estates
 	| EstateName    | OperatorName    | 
diff --git a/TransactionProcessor.IntegrationTests/Features/Merchant.feature b/TransactionProcessor.IntegrationTests/Features/Merchant.feature
index 81f9dd2d..6cb90522 100644
--- a/TransactionProcessor.IntegrationTests/Features/Merchant.feature
+++ b/TransactionProcessor.IntegrationTests/Features/Merchant.feature
@@ -32,8 +32,8 @@ Background:
 
 	Given I have created the following operators
 	| EstateName    | OperatorName    | RequireCustomMerchantNumber | RequireCustomTerminalNumber |
-	| Test Estate 1 | Test Operator 1 | True                        | True                        |
-	| Test Estate 2 | Test Operator 1 | True                        | True                        |
+	| Test Estate 1 | Test Operator 1 | False                        | False                        |
+	| Test Estate 2 | Test Operator 1 | False                        | False                        |
 
 	And I have assigned the following operators to the estates
 	| EstateName    | OperatorName    | 
diff --git a/TransactionProcessor.IntegrationTests/Features/ReconciliationFeature.feature b/TransactionProcessor.IntegrationTests/Features/ReconciliationFeature.feature
index a0cb1f27..d3afa433 100644
--- a/TransactionProcessor.IntegrationTests/Features/ReconciliationFeature.feature
+++ b/TransactionProcessor.IntegrationTests/Features/ReconciliationFeature.feature
@@ -28,8 +28,8 @@ Background:
 
 	Given I have created the following operators
 	| EstateName    | OperatorName | RequireCustomMerchantNumber | RequireCustomTerminalNumber |
-	| Test Estate 1 | Safaricom    | True                        | True                        |
-	| Test Estate 2 | Safaricom    | True                        | True                        |
+	| Test Estate 1 | Safaricom    | False                        | False                        |
+	| Test Estate 2 | Safaricom    | False                        | False                        |
 
 	And I have assigned the following operators to the estates
 	| EstateName    | OperatorName    | 
diff --git a/TransactionProcessor.IntegrationTests/Features/RedeemVoucher.feature b/TransactionProcessor.IntegrationTests/Features/RedeemVoucher.feature
index 7957dfab..f8a057c4 100644
--- a/TransactionProcessor.IntegrationTests/Features/RedeemVoucher.feature
+++ b/TransactionProcessor.IntegrationTests/Features/RedeemVoucher.feature
@@ -29,7 +29,7 @@ Background:
 
 	Given I have created the following operators
 	| EstateName    | OperatorName     | RequireCustomMerchantNumber | RequireCustomTerminalNumber |
-	| Test Estate 1 | Voucher          | True                        | True                        |
+	| Test Estate 1 | Voucher          | False                        | False                        |
 
 	And I have assigned the following operators to the estates
 	| EstateName    | OperatorName    | 
diff --git a/TransactionProcessor.IntegrationTests/Features/SaleTransactionFeature.feature b/TransactionProcessor.IntegrationTests/Features/SaleTransactionFeature.feature
index b923a6e4..534b338a 100644
--- a/TransactionProcessor.IntegrationTests/Features/SaleTransactionFeature.feature
+++ b/TransactionProcessor.IntegrationTests/Features/SaleTransactionFeature.feature
@@ -45,10 +45,10 @@ Background:
 
 	Given I have created the following operators
 	| EstateName    | OperatorName     | RequireCustomMerchantNumber | RequireCustomTerminalNumber |
-	| Test Estate 1 | Safaricom        | True                        | True                        |
-	| Test Estate 1 | Voucher          | True                        | True                        |
-	| Test Estate 1 | PataPawa PostPay | True                        | True                        |
-	| Test Estate 1 | PataPawa PrePay | True                        | True                        |
+	| Test Estate 1 | Safaricom        | False                        | False                        |
+	| Test Estate 1 | Voucher          | False                        | False                        |
+	| Test Estate 1 | PataPawa PostPay | False                        | False                        |
+	| Test Estate 1 | PataPawa PrePay | False                        | False                        |
 		
 	And I have assigned the following operators to the estates
 	| EstateName    | OperatorName    | 
diff --git a/TransactionProcessor.IntegrationTests/Features/Settlement.feature b/TransactionProcessor.IntegrationTests/Features/Settlement.feature
index 6f4fa338..4fa24d21 100644
--- a/TransactionProcessor.IntegrationTests/Features/Settlement.feature
+++ b/TransactionProcessor.IntegrationTests/Features/Settlement.feature
@@ -29,8 +29,8 @@ Background:
 
 	Given I have created the following operators
 	| EstateName    | OperatorName | RequireCustomMerchantNumber | RequireCustomTerminalNumber |
-	| Test Estate 1 | Safaricom    | True                        | True                        |
-	| Test Estate 1 | Voucher    | True                        | True                        |
+	| Test Estate 1 | Safaricom    | False                        | False                        |
+	| Test Estate 1 | Voucher    | False                        | False                        |
 
 	And I have assigned the following operators to the estates
 	| EstateName    | OperatorName    | 
diff --git a/TransactionProcessor.IntegrationTests/Features/SettlementReporting.feature b/TransactionProcessor.IntegrationTests/Features/SettlementReporting.feature
index 62066586..4ef3906d 100644
--- a/TransactionProcessor.IntegrationTests/Features/SettlementReporting.feature
+++ b/TransactionProcessor.IntegrationTests/Features/SettlementReporting.feature
@@ -28,8 +28,8 @@ Background:
 
 	Given I have created the following operators
 	| EstateName    | OperatorName | RequireCustomMerchantNumber | RequireCustomTerminalNumber |
-	| Test Estate 1 | Safaricom    | True                        | True                        |
-	| Test Estate 2 | Safaricom    | True                        | True                        |
+	| Test Estate 1 | Safaricom    | False                        | False                        |
+	| Test Estate 2 | Safaricom    | False                        | False                        |
 
 	And I have assigned the following operators to the estates
 	| EstateName    | OperatorName    |