diff --git a/src/main/java/seedu/address/logic/commands/DeleteCommand.java b/src/main/java/seedu/address/logic/commands/DeleteCommand.java
index 360303a8fc66..d4d3ca82369b 100644
--- a/src/main/java/seedu/address/logic/commands/DeleteCommand.java
+++ b/src/main/java/seedu/address/logic/commands/DeleteCommand.java
@@ -6,7 +6,6 @@
 import seedu.address.commons.core.index.Index;
 import seedu.address.logic.commands.exceptions.CommandException;
 import seedu.address.model.person.Person;
-import seedu.address.model.person.exceptions.PersonNotFoundException;
 
 /**
  * Deletes a person identified using it's displayed index from the address book.
@@ -37,14 +36,8 @@ public CommandResult execute() throws CommandException {
         }
 
         Person personToDelete = lastShownList.get(targetIndex.getZeroBased());
-
-        try {
-            model.deletePerson(personToDelete);
-            model.commitAddressBook();
-        } catch (PersonNotFoundException pnfe) {
-            throw new AssertionError("The target person cannot be missing", pnfe);
-        }
-
+        model.deletePerson(personToDelete);
+        model.commitAddressBook();
         return new CommandResult(String.format(MESSAGE_DELETE_PERSON_SUCCESS, personToDelete));
     }
 
diff --git a/src/main/java/seedu/address/logic/commands/EditCommand.java b/src/main/java/seedu/address/logic/commands/EditCommand.java
index 5d79efe7e246..f13f7d1c69e9 100644
--- a/src/main/java/seedu/address/logic/commands/EditCommand.java
+++ b/src/main/java/seedu/address/logic/commands/EditCommand.java
@@ -23,7 +23,6 @@
 import seedu.address.model.person.Name;
 import seedu.address.model.person.Person;
 import seedu.address.model.person.Phone;
-import seedu.address.model.person.exceptions.PersonNotFoundException;
 import seedu.address.model.tag.Tag;
 
 /**
@@ -80,11 +79,7 @@ public CommandResult execute() throws CommandException {
             throw new CommandException(MESSAGE_DUPLICATE_PERSON);
         }
 
-        try {
-            model.updatePerson(personToEdit, editedPerson);
-        } catch (PersonNotFoundException pnfe) {
-            throw new AssertionError("The target person cannot be missing", pnfe);
-        }
+        model.updatePerson(personToEdit, editedPerson);
         model.updateFilteredPersonList(PREDICATE_SHOW_ALL_PERSONS);
         model.commitAddressBook();
         return new CommandResult(String.format(MESSAGE_EDIT_PERSON_SUCCESS, editedPerson));
diff --git a/src/main/java/seedu/address/model/AddressBook.java b/src/main/java/seedu/address/model/AddressBook.java
index 2c4c06ddbb28..0c9a902a8843 100644
--- a/src/main/java/seedu/address/model/AddressBook.java
+++ b/src/main/java/seedu/address/model/AddressBook.java
@@ -7,7 +7,6 @@
 import javafx.collections.ObservableList;
 import seedu.address.model.person.Person;
 import seedu.address.model.person.UniquePersonList;
-import seedu.address.model.person.exceptions.PersonNotFoundException;
 
 /**
  * Wraps all data at the address-book level
@@ -77,11 +76,10 @@ public void addPerson(Person p) {
 
     /**
      * Replaces the given person {@code target} in the list with {@code editedPerson}.
+     * {@code target} must exist in the address book.
      * The person identity of {@code editedPerson} must not be the same as another existing person in the address book.
-     *
-     * @throws PersonNotFoundException if {@code target} could not be found in the list.
      */
-    public void updatePerson(Person target, Person editedPerson) throws PersonNotFoundException {
+    public void updatePerson(Person target, Person editedPerson) {
         requireNonNull(editedPerson);
 
         persons.setPerson(target, editedPerson);
@@ -89,9 +87,9 @@ public void updatePerson(Person target, Person editedPerson) throws PersonNotFou
 
     /**
      * Removes {@code key} from this {@code AddressBook}.
-     * @throws PersonNotFoundException if the {@code key} is not in this {@code AddressBook}.
+     * {@code key} must exist in the address book.
      */
-    public void removePerson(Person key) throws PersonNotFoundException {
+    public void removePerson(Person key) {
         persons.remove(key);
     }
 
diff --git a/src/main/java/seedu/address/model/Model.java b/src/main/java/seedu/address/model/Model.java
index fe6ad8333305..ac4521f33199 100644
--- a/src/main/java/seedu/address/model/Model.java
+++ b/src/main/java/seedu/address/model/Model.java
@@ -4,7 +4,6 @@
 
 import javafx.collections.ObservableList;
 import seedu.address.model.person.Person;
-import seedu.address.model.person.exceptions.PersonNotFoundException;
 
 /**
  * The API of the Model component.
@@ -24,8 +23,11 @@ public interface Model {
      */
     boolean hasPerson(Person person);
 
-    /** Deletes the given person. */
-    void deletePerson(Person target) throws PersonNotFoundException;
+    /**
+     * Deletes the given person.
+     * The person must exist in the address book.
+     */
+    void deletePerson(Person target);
 
     /**
      * Adds the given person.
@@ -35,11 +37,10 @@ public interface Model {
 
     /**
      * Replaces the given person {@code target} with {@code editedPerson}.
+     * {@code target} must exist in the address book.
      * The person identity of {@code editedPerson} must not be the same as another existing person in the address book.
-     *
-     * @throws PersonNotFoundException if {@code target} could not be found in the list.
      */
-    void updatePerson(Person target, Person editedPerson) throws PersonNotFoundException;
+    void updatePerson(Person target, Person editedPerson);
 
     /** Returns an unmodifiable view of the filtered person list */
     ObservableList<Person> getFilteredPersonList();
diff --git a/src/main/java/seedu/address/model/ModelManager.java b/src/main/java/seedu/address/model/ModelManager.java
index 913cb6864377..b6063a769ff9 100644
--- a/src/main/java/seedu/address/model/ModelManager.java
+++ b/src/main/java/seedu/address/model/ModelManager.java
@@ -13,7 +13,6 @@
 import seedu.address.commons.core.LogsCenter;
 import seedu.address.commons.events.model.AddressBookChangedEvent;
 import seedu.address.model.person.Person;
-import seedu.address.model.person.exceptions.PersonNotFoundException;
 
 /**
  * Represents the in-memory model of the address book data.
@@ -65,7 +64,7 @@ public synchronized boolean hasPerson(Person person) {
     }
 
     @Override
-    public synchronized void deletePerson(Person target) throws PersonNotFoundException {
+    public synchronized void deletePerson(Person target) {
         versionedAddressBook.removePerson(target);
         indicateAddressBookChanged();
     }
@@ -78,7 +77,7 @@ public synchronized void addPerson(Person person) {
     }
 
     @Override
-    public void updatePerson(Person target, Person editedPerson) throws PersonNotFoundException {
+    public void updatePerson(Person target, Person editedPerson) {
         requireAllNonNull(target, editedPerson);
 
         versionedAddressBook.updatePerson(target, editedPerson);
diff --git a/src/main/java/seedu/address/model/person/UniquePersonList.java b/src/main/java/seedu/address/model/person/UniquePersonList.java
index 71dc1043651e..65840f3fb0c2 100644
--- a/src/main/java/seedu/address/model/person/UniquePersonList.java
+++ b/src/main/java/seedu/address/model/person/UniquePersonList.java
@@ -48,11 +48,10 @@ public void add(Person toAdd) {
 
     /**
      * Replaces the person {@code target} in the list with {@code editedPerson}.
+     * {@code target} must exist in the list.
      * The person identity of {@code editedPerson} must not be the same as another existing person in the list.
-     *
-     * @throws PersonNotFoundException if {@code target} could not be found in the list.
      */
-    public void setPerson(Person target, Person editedPerson) throws PersonNotFoundException {
+    public void setPerson(Person target, Person editedPerson) {
         requireNonNull(editedPerson);
 
         int index = internalList.indexOf(target);
@@ -69,10 +68,9 @@ public void setPerson(Person target, Person editedPerson) throws PersonNotFoundE
 
     /**
      * Removes the equivalent person from the list.
-     *
-     * @throws PersonNotFoundException if no such person could be found in the list.
+     * The person must exist in the list.
      */
-    public void remove(Person toRemove) throws PersonNotFoundException {
+    public void remove(Person toRemove) {
         requireNonNull(toRemove);
         if (!internalList.remove(toRemove)) {
             throw new PersonNotFoundException();
diff --git a/src/main/java/seedu/address/model/person/exceptions/PersonNotFoundException.java b/src/main/java/seedu/address/model/person/exceptions/PersonNotFoundException.java
index f757e25f5566..fa764426ca73 100644
--- a/src/main/java/seedu/address/model/person/exceptions/PersonNotFoundException.java
+++ b/src/main/java/seedu/address/model/person/exceptions/PersonNotFoundException.java
@@ -3,4 +3,4 @@
 /**
  * Signals that the operation is unable to find the specified person.
  */
-public class PersonNotFoundException extends Exception {}
+public class PersonNotFoundException extends RuntimeException {}
diff --git a/src/test/java/seedu/address/logic/commands/CommandTestUtil.java b/src/test/java/seedu/address/logic/commands/CommandTestUtil.java
index 32964d022a42..870797d66d83 100644
--- a/src/test/java/seedu/address/logic/commands/CommandTestUtil.java
+++ b/src/test/java/seedu/address/logic/commands/CommandTestUtil.java
@@ -19,7 +19,6 @@
 import seedu.address.model.Model;
 import seedu.address.model.person.NameContainsKeywordsPredicate;
 import seedu.address.model.person.Person;
-import seedu.address.model.person.exceptions.PersonNotFoundException;
 import seedu.address.testutil.EditPersonDescriptorBuilder;
 
 /**
@@ -127,12 +126,8 @@ public static void showPersonAtIndex(Model model, Index targetIndex) {
      */
     public static void deleteFirstPerson(Model model) {
         Person firstPerson = model.getFilteredPersonList().get(0);
-        try {
-            model.deletePerson(firstPerson);
-            model.commitAddressBook();
-        } catch (PersonNotFoundException pnfe) {
-            throw new AssertionError("Person in filtered list must exist in model.", pnfe);
-        }
+        model.deletePerson(firstPerson);
+        model.commitAddressBook();
     }
 
     /**
diff --git a/src/test/java/seedu/address/logic/commands/DeleteCommandTest.java b/src/test/java/seedu/address/logic/commands/DeleteCommandTest.java
index dab1a682a43e..a25f3b30a98b 100644
--- a/src/test/java/seedu/address/logic/commands/DeleteCommandTest.java
+++ b/src/test/java/seedu/address/logic/commands/DeleteCommandTest.java
@@ -31,7 +31,7 @@ public class DeleteCommandTest {
     private Model model = new ModelManager(getTypicalAddressBook(), new UserPrefs());
 
     @Test
-    public void execute_validIndexUnfilteredList_success() throws Exception {
+    public void execute_validIndexUnfilteredList_success() {
         Person personToDelete = model.getFilteredPersonList().get(INDEX_FIRST_PERSON.getZeroBased());
         DeleteCommand deleteCommand = prepareCommand(INDEX_FIRST_PERSON);
 
@@ -53,7 +53,7 @@ public void execute_invalidIndexUnfilteredList_throwsCommandException() {
     }
 
     @Test
-    public void execute_validIndexFilteredList_success() throws Exception {
+    public void execute_validIndexFilteredList_success() {
         showPersonAtIndex(model, INDEX_FIRST_PERSON);
 
         Person personToDelete = model.getFilteredPersonList().get(INDEX_FIRST_PERSON.getZeroBased());
diff --git a/src/test/java/seedu/address/logic/commands/EditCommandTest.java b/src/test/java/seedu/address/logic/commands/EditCommandTest.java
index 06612527d891..27c2947b591a 100644
--- a/src/test/java/seedu/address/logic/commands/EditCommandTest.java
+++ b/src/test/java/seedu/address/logic/commands/EditCommandTest.java
@@ -39,7 +39,7 @@ public class EditCommandTest {
     private Model model = new ModelManager(getTypicalAddressBook(), new UserPrefs());
 
     @Test
-    public void execute_allFieldsSpecifiedUnfilteredList_success() throws Exception {
+    public void execute_allFieldsSpecifiedUnfilteredList_success() {
         Person editedPerson = new PersonBuilder().build();
         EditPersonDescriptor descriptor = new EditPersonDescriptorBuilder(editedPerson).build();
         EditCommand editCommand = prepareCommand(INDEX_FIRST_PERSON, descriptor);
@@ -54,7 +54,7 @@ public void execute_allFieldsSpecifiedUnfilteredList_success() throws Exception
     }
 
     @Test
-    public void execute_someFieldsSpecifiedUnfilteredList_success() throws Exception {
+    public void execute_someFieldsSpecifiedUnfilteredList_success() {
         Index indexLastPerson = Index.fromOneBased(model.getFilteredPersonList().size());
         Person lastPerson = model.getFilteredPersonList().get(indexLastPerson.getZeroBased());
 
@@ -89,7 +89,7 @@ public void execute_noFieldSpecifiedUnfilteredList_success() {
     }
 
     @Test
-    public void execute_filteredList_success() throws Exception {
+    public void execute_filteredList_success() {
         showPersonAtIndex(model, INDEX_FIRST_PERSON);
 
         Person personInFilteredList = model.getFilteredPersonList().get(INDEX_FIRST_PERSON.getZeroBased());
diff --git a/src/test/java/systemtests/DeleteCommandSystemTest.java b/src/test/java/systemtests/DeleteCommandSystemTest.java
index 97d42add1209..29fbb5fc3930 100644
--- a/src/test/java/systemtests/DeleteCommandSystemTest.java
+++ b/src/test/java/systemtests/DeleteCommandSystemTest.java
@@ -19,7 +19,6 @@
 import seedu.address.logic.commands.UndoCommand;
 import seedu.address.model.Model;
 import seedu.address.model.person.Person;
-import seedu.address.model.person.exceptions.PersonNotFoundException;
 
 public class DeleteCommandSystemTest extends AddressBookSystemTest {
 
@@ -118,11 +117,7 @@ public void delete() {
      */
     private Person removePerson(Model model, Index index) {
         Person targetPerson = getPerson(model, index);
-        try {
-            model.deletePerson(targetPerson);
-        } catch (PersonNotFoundException pnfe) {
-            throw new AssertionError("targetPerson is retrieved from model.", pnfe);
-        }
+        model.deletePerson(targetPerson);
         return targetPerson;
     }
 
diff --git a/src/test/java/systemtests/EditCommandSystemTest.java b/src/test/java/systemtests/EditCommandSystemTest.java
index 6547b0dbc3df..9e9e4572ddb2 100644
--- a/src/test/java/systemtests/EditCommandSystemTest.java
+++ b/src/test/java/systemtests/EditCommandSystemTest.java
@@ -44,7 +44,6 @@
 import seedu.address.model.person.Name;
 import seedu.address.model.person.Person;
 import seedu.address.model.person.Phone;
-import seedu.address.model.person.exceptions.PersonNotFoundException;
 import seedu.address.model.tag.Tag;
 import seedu.address.testutil.PersonBuilder;
 import seedu.address.testutil.PersonUtil;
@@ -52,7 +51,7 @@
 public class EditCommandSystemTest extends AddressBookSystemTest {
 
     @Test
-    public void edit() throws Exception {
+    public void edit() {
         Model model = getModel();
 
         /* ----------------- Performing edit operation while an unfiltered list is being shown ---------------------- */
@@ -235,13 +234,8 @@ private void assertCommandSuccess(String command, Index toEdit, Person editedPer
     private void assertCommandSuccess(String command, Index toEdit, Person editedPerson,
             Index expectedSelectedCardIndex) {
         Model expectedModel = getModel();
-        try {
-            expectedModel.updatePerson(
-                    expectedModel.getFilteredPersonList().get(toEdit.getZeroBased()), editedPerson);
-            expectedModel.updateFilteredPersonList(PREDICATE_SHOW_ALL_PERSONS);
-        } catch (PersonNotFoundException e) {
-            throw new IllegalArgumentException("editedPerson isn't found in the model.", e);
-        }
+        expectedModel.updatePerson(expectedModel.getFilteredPersonList().get(toEdit.getZeroBased()), editedPerson);
+        expectedModel.updateFilteredPersonList(PREDICATE_SHOW_ALL_PERSONS);
 
         assertCommandSuccess(command, expectedModel,
                 String.format(EditCommand.MESSAGE_EDIT_PERSON_SUCCESS, editedPerson), expectedSelectedCardIndex);