diff --git a/src/main/java/seedu/foodrem/logic/commands/tagcommands/TagCommandUtil.java b/src/main/java/seedu/foodrem/logic/commands/tagcommands/TagCommandUtil.java
index e61a0f323b6..7458b1ed5a7 100644
--- a/src/main/java/seedu/foodrem/logic/commands/tagcommands/TagCommandUtil.java
+++ b/src/main/java/seedu/foodrem/logic/commands/tagcommands/TagCommandUtil.java
@@ -25,6 +25,8 @@ private TagCommandUtil() {}
      */
     public static Item validateAndGetItem(Model model, Tag tag, Index index) throws CommandException {
         requireNonNull(model);
+        requireNonNull(tag);
+        requireNonNull(index);
 
         if (!model.hasTag(tag)) {
             throw new CommandException("This tag does not exist");
diff --git a/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/RenameTagCommandParser.java b/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/RenameTagCommandParser.java
index 1a0aa5283ef..fd2343d8452 100644
--- a/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/RenameTagCommandParser.java
+++ b/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/RenameTagCommandParser.java
@@ -52,6 +52,7 @@ public RenameTagCommand parse(String args) throws ParseException {
     }
 
     private boolean hasExtraPrefixesInName(String name) {
+        assert name != null;
         Matcher matcher = CliSyntax.PREFIX_REGEX.matcher(name);
         return matcher.find();
     }
diff --git a/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/TagCommandParser.java b/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/TagCommandParser.java
index f8cbb62d147..d1741dcec6b 100644
--- a/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/TagCommandParser.java
+++ b/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/TagCommandParser.java
@@ -2,8 +2,6 @@
 
 import static java.util.Objects.requireNonNull;
 
-import java.util.stream.Stream;
-
 import seedu.foodrem.commons.core.Messages;
 import seedu.foodrem.commons.core.index.Index;
 import seedu.foodrem.commons.util.StringUtil;
@@ -13,7 +11,6 @@
 import seedu.foodrem.logic.parser.CliSyntax;
 import seedu.foodrem.logic.parser.Parser;
 import seedu.foodrem.logic.parser.ParserUtil;
-import seedu.foodrem.logic.parser.Prefix;
 import seedu.foodrem.logic.parser.exceptions.ParseException;
 
 /**
@@ -32,7 +29,7 @@ public TagCommand parse(String args) throws ParseException {
         Index index = StringUtil.validateAndGetIndexFromString(argMultimap.getPreamble().trim(),
                                                                TagCommand.getUsage());
 
-        if (!arePrefixesPresent(argMultimap, CliSyntax.PREFIX_NAME)
+        if (!ParserUtil.arePrefixesPresent(argMultimap, CliSyntax.PREFIX_NAME)
                 || argMultimap.getPreamble().isEmpty()) {
             throw new ParseException(String.format(Messages.MESSAGE_INVALID_COMMAND_FORMAT, TagCommand.getUsage()));
         }
@@ -42,11 +39,4 @@ public TagCommand parse(String args) throws ParseException {
         return new TagCommand(name, index);
     }
 
-    /**
-     * Returns {@code true} if none of the prefixes contains empty {@code Optional} values in the given
-     * {@code ArgumentMultimap}.
-     */
-    private static boolean arePrefixesPresent(ArgumentMultimap argumentMultimap, Prefix... prefixes) {
-        return Stream.of(prefixes).allMatch(prefix -> argumentMultimap.getValue(prefix).isPresent());
-    }
 }
diff --git a/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/UntagCommandParser.java b/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/UntagCommandParser.java
index c4f030c2cc5..a67d3f1bf46 100644
--- a/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/UntagCommandParser.java
+++ b/src/main/java/seedu/foodrem/logic/parser/tagcommandparser/UntagCommandParser.java
@@ -1,7 +1,6 @@
 package seedu.foodrem.logic.parser.tagcommandparser;
 
 import static java.util.Objects.requireNonNull;
-import static seedu.foodrem.logic.parser.ParserUtil.arePrefixesPresent;
 
 import seedu.foodrem.commons.core.Messages;
 import seedu.foodrem.commons.core.index.Index;
@@ -29,7 +28,7 @@ public UntagCommand parse(String args) throws ParseException {
         ArgumentMultimap argMultimap = ArgumentTokenizer.tokenize(args, CliSyntax.PREFIX_NAME);
         Index index = StringUtil.validateAndGetIndexFromString(argMultimap.getPreamble().trim(),
                                                                UntagCommand.getUsage());
-        if (!arePrefixesPresent(argMultimap, CliSyntax.PREFIX_NAME)
+        if (!ParserUtil.arePrefixesPresent(argMultimap, CliSyntax.PREFIX_NAME)
                 || argMultimap.getPreamble().isEmpty()) {
             throw new ParseException(String.format(Messages.MESSAGE_INVALID_COMMAND_FORMAT, UntagCommand.getUsage()));
         }
diff --git a/src/main/java/seedu/foodrem/model/tag/Tag.java b/src/main/java/seedu/foodrem/model/tag/Tag.java
index c58672c722f..d8316848811 100644
--- a/src/main/java/seedu/foodrem/model/tag/Tag.java
+++ b/src/main/java/seedu/foodrem/model/tag/Tag.java
@@ -21,16 +21,22 @@ public Tag(String tagName) {
     }
 
     public String getName() {
+        assert tagName != null;
         return this.tagName.toString();
     }
 
+    /**
+     * @inheritDoc
+     */
     @Override
     public boolean equals(Object other) {
         return other == this
             || (other instanceof Tag
             && tagName.equals(((Tag) other).tagName));
     }
-
+    /**
+     * @inheritDoc
+     */
     @Override
     public int hashCode() {
         return tagName.hashCode();
diff --git a/src/main/java/seedu/foodrem/model/tag/TagName.java b/src/main/java/seedu/foodrem/model/tag/TagName.java
index 225cf84abb6..cb902db693e 100644
--- a/src/main/java/seedu/foodrem/model/tag/TagName.java
+++ b/src/main/java/seedu/foodrem/model/tag/TagName.java
@@ -37,11 +37,17 @@ public TagName(String name) {
         fullName = name;
     }
 
+    /**
+     * @inheritDoc
+     */
     @Override
     public String toString() {
         return fullName;
     }
 
+    /**
+     * @inheritDoc
+     */
     @Override
     public boolean equals(Object other) {
         return other == this
@@ -49,6 +55,9 @@ public boolean equals(Object other) {
                 && fullName.equals(((TagName) other).fullName));
     }
 
+    /**
+     * @inheritDoc
+     */
     @Override
     public int hashCode() {
         return fullName.hashCode();
diff --git a/src/main/java/seedu/foodrem/model/tag/TagNameContainsKeywordsPredicate.java b/src/main/java/seedu/foodrem/model/tag/TagNameContainsKeywordsPredicate.java
index fdca44606e5..0c7100750e6 100644
--- a/src/main/java/seedu/foodrem/model/tag/TagNameContainsKeywordsPredicate.java
+++ b/src/main/java/seedu/foodrem/model/tag/TagNameContainsKeywordsPredicate.java
@@ -15,12 +15,21 @@ public TagNameContainsKeywordsPredicate(List<String> keywords) {
         this.keywords = keywords;
     }
 
+    /**
+     * Tests whether the keyword is contained in the {@code tag}
+     *
+     * @param tag to be tested
+     * @return boolean stating whether keyword in tag name
+     */
     @Override
     public boolean test(Tag tag) {
         return keywords.stream()
                 .anyMatch(keyword -> StringUtil.containsWordIgnoreCase(tag.getName(), keyword));
     }
 
+    /**
+     * @inheritDoc
+     */
     @Override
     public boolean equals(Object other) {
         return other == this
diff --git a/src/main/java/seedu/foodrem/model/tag/exceptions/DuplicateTagException.java b/src/main/java/seedu/foodrem/model/tag/exceptions/DuplicateTagException.java
index b8e6f9ae2f6..4ea45fd8d4c 100644
--- a/src/main/java/seedu/foodrem/model/tag/exceptions/DuplicateTagException.java
+++ b/src/main/java/seedu/foodrem/model/tag/exceptions/DuplicateTagException.java
@@ -5,6 +5,9 @@
  * name).
  */
 public class DuplicateTagException extends RuntimeException {
+    /**
+     * Creates a new DuplicateTagException
+     */
     public DuplicateTagException() {
         super("Operation would result in duplicate tags");
     }