[{"Employee":{"EmployeeData":{"basePay":"1000","sumPayAmount":"2000"}}},{"Employee":{"EmployeeData":{"basePay":"4000","sumPayAmount":"1000"}}}]

db.collection.find({$expr:{$gt:[{$toDecimal:"$Employee.EmployeeData.basePay"},{$toDecimal:"$Employee.EmployeeData.sumPayAmount"}]}})