diff --git a/WordPressVIPMinimum/Sniffs/Filters/AlwaysReturnSniff.php b/WordPressVIPMinimum/Sniffs/Filters/AlwaysReturnSniff.php
new file mode 100644
index 00000000..95e6fe19
--- /dev/null
+++ b/WordPressVIPMinimum/Sniffs/Filters/AlwaysReturnSniff.php
@@ -0,0 +1,301 @@
+<?php
+/**
+ * WordPressVIPMinimum Coding Standard.
+ *
+ * @package VIPCS\WordPressVIPMinimum
+ */
+
+namespace WordPressVIPMinimum\Sniffs\Filters;
+
+use PHP_CodeSniffer_File as File;
+use PHP_CodeSniffer_Tokens as Tokens;
+
+/**
+ * This sniff validates that filters always return a value
+ *
+ * @package VIPCS\WordPressVIPMinimum
+ */
+class AlwaysReturnSniff implements \PHP_CodeSniffer_Sniff {
+
+	/**
+	 * The tokens of the phpcsFile.
+	 *
+	 * @var array
+	 */
+	private $tokens;
+
+	/**
+	 * The phpcsFile.
+	 *
+	 * @var phpcsFile
+	 */
+	private $phpcsFile;
+
+	/**
+	 * Filter name pointer.
+	 *
+	 * @var int
+	 */
+	private $filterNamePtr;
+
+	/**
+	 * Returns the token types that this sniff is interested in.
+	 *
+	 * @return array(int)
+	 */
+	public function register() {
+		return Tokens::$functionNameTokens;
+
+	}//end register()
+
+	/**
+	 * Processes the tokens that this sniff is interested in.
+	 *
+	 * @param \PHP_CodeSniffer\Files\File $phpcsFile The file where the token was found.
+	 * @param int                         $stackPtr  The position in the stack where
+	 *                                               the token was found.
+	 *
+	 * @return void
+	 */
+	public function process( File $phpcsFile, $stackPtr ) {
+
+		$this->tokens = $phpcsFile->getTokens();
+
+		$this->phpcsFile = $phpcsFile;
+
+		$functionName = $this->tokens[ $stackPtr ]['content'];
+
+		if ( 'add_filter' !== $functionName ) {
+			return;
+		}
+
+		$this->filterNamePtr = $this->phpcsFile->findNext(
+			array_merge( Tokens::$emptyTokens, array( T_OPEN_PARENTHESIS ) ), // types.
+			$stackPtr + 1, // start.
+			null, // end.
+			true, // exclude.
+			null, // value.
+			true // local.
+		);
+
+		if ( ! $this->filterNamePtr ) {
+			// Something is wrong.
+			return;
+		}
+
+		$callbackPtr = $this->phpcsFile->findNext(
+			array_merge( Tokens::$emptyTokens, array( T_COMMA ) ), // types.
+			$this->filterNamePtr + 1, // start.
+			null, // end.
+			true, // exclude.
+			null, // value.
+			true // local.
+		);
+
+		if ( ! $callbackPtr ) {
+			// Something is wrong.
+			return;
+		}
+
+		if ( 'PHPCS_T_CLOSURE' === $this->tokens[ $callbackPtr ]['code'] ) {
+			$this->processFunctionBody( $callbackPtr );
+		} elseif ( 'T_ARRAY' === $this->tokens[ $callbackPtr ]['type'] ) {
+			$this->processArray( $callbackPtr );
+		} elseif ( true === in_array( $this->tokens[ $callbackPtr ]['code'], Tokens::$stringTokens, true ) ) {
+			$this->processString( $callbackPtr );
+		}
+
+	}
+
+	/**
+	 * Process array.
+	 *
+	 * @param int $stackPtr The position in the stack where the token was found.
+	 */
+	private function processArray( $stackPtr ) {
+
+		$previous = $this->phpcsFile->findPrevious(
+			Tokens::$emptyTokens, // types.
+			$this->tokens[ $stackPtr ]['parenthesis_closer'] - 1, // start.
+			null, // end.
+			true, // exclude.
+			null, // value.
+			false // local.
+		);
+
+		if ( true === in_array( T_CLASS, $this->tokens[ $stackPtr ]['conditions'], true ) ) {
+			$classPtr = array_search( T_CLASS, $this->tokens[ $stackPtr ]['conditions'], true );
+			if ( $classPtr ) {
+				$classToken = $this->tokens[ $classPtr ];
+				$this->processString( $previous, $classToken['scope_opener'], $classToken['scope_closer'] );
+				return;
+			}
+		}
+
+		$this->processString( $previous );
+
+	}
+
+	/**
+	 * Process string.
+	 *
+	 * @param int $stackPtr The position in the stack where the token was found.
+	 * @param int $start The start of the token.
+	 * @param int $end The end of the token.
+	 */
+	private function processString( $stackPtr, $start = 0, $end = null ) {
+
+		$callbackFunctionName = substr( $this->tokens[ $stackPtr ]['content'], 1, -1 );
+
+		$callbackFunctionPtr = $this->phpcsFile->findNext(
+			Tokens::$functionNameTokens, // types.
+			$start, // start.
+			$end, // end.
+			false, // exclude.
+			$callbackFunctionName, // value.
+			false // local.
+		);
+
+		if ( ! $callbackFunctionPtr ) {
+			// We were not able to find the function callback in the file.
+			return;
+		}
+
+		$this->processFunction( $callbackFunctionPtr, $start, $end );
+
+	}
+
+	/**
+	 * Process function.
+	 *
+	 * @param int $stackPtr The position in the stack where the token was found.
+	 * @param int $start The start of the token.
+	 * @param int $end The end of the token.
+	 */
+	private function processFunction( $stackPtr, $start = 0, $end = null ) {
+
+		$functionName = $this->tokens[ $stackPtr ]['content'];
+
+		$offset = $start;
+		while ( $functionStackPtr = $this->phpcsFile->findNext( array( T_FUNCTION ), $offset, $end, false, null, false ) ) {
+			$functionNamePtr = $this->phpcsFile->findNext( Tokens::$emptyTokens, $functionStackPtr + 1, null, true, null, true );
+			if ( T_STRING === $this->tokens[ $functionNamePtr ]['code'] ) {
+				if ( $this->tokens[ $functionNamePtr ]['content'] === $functionName ) {
+					$this->processFunctionBody( $functionStackPtr );
+					return;
+				}
+			}
+			$offset = $functionStackPtr + 1;
+		}
+	}
+
+	/**
+	 * Process function's body
+	 *
+	 * @param int $stackPtr The position in the stack where the token was found.
+	 */
+	private function processFunctionBody( $stackPtr ) {
+
+		$filterName = $this->tokens[ $this->filterNamePtr ]['content'];
+
+		$functionBodyScopeStart = $this->tokens[ $stackPtr ]['scope_opener'];
+		$functionBodyScopeEnd   = $this->tokens[ $stackPtr ]['scope_closer'];
+
+		$returnTokenPtr = $this->phpcsFile->findNext(
+			array( T_RETURN ), // types.
+			( $functionBodyScopeStart + 1 ), // start.
+			$functionBodyScopeEnd, // end.
+			false, // exclude.
+			null, // value.
+			false // local.
+		);
+
+		$insideIfConditionalReturn = 0;
+		$outsideConditionalReturn  = 0;
+
+		while ( $returnTokenPtr ) {
+			if ( $this->isInsideIfConditonal( $returnTokenPtr ) ) {
+				$insideIfConditionalReturn++;
+			} else {
+				$outsideConditionalReturn++;
+			}
+			if ( $this->isReturningVoid( $returnTokenPtr ) ) {
+				$this->phpcsFile->AddWarning( sprintf( 'Please, make sure that a callback to `%s` filter is returnin void intentionally.', $filterName ), $functionBodyScopeStart, 'voidReturn' );
+			}
+			$returnTokenPtr = $this->phpcsFile->findNext(
+				array( T_RETURN ), // types.
+				( $returnTokenPtr + 1 ), // start.
+				$functionBodyScopeEnd, // end.
+				false, // exclude.
+				null, // value.
+				false // local.
+			);
+		}
+
+		if ( 0 < $insideIfConditionalReturn && 0 === $outsideConditionalReturn ) {
+			$this->phpcsFile->AddWarning( sprintf( 'Please, make sure that a callback to `%s` filter is always returning some value.', $filterName ), $functionBodyScopeStart, 'missingReturnStatement' );
+		}
+
+	}
+
+	/**
+	 * Is the current token inside a conditional?
+	 *
+	 * @param int $stackPtr The position in the stack where the token was found.
+	 *
+	 * @return bool
+	 */
+	private function isInsideIfConditonal( $stackPtr ) {
+
+		// This check helps us in situations a class or a function is wrapped
+		// inside a conditional as a whole. Eg.: inside `class_exists`.
+		if ( T_FUNCTION === end( $this->tokens[ $stackPtr ]['conditions'] ) ) {
+			return false;
+		}
+
+		// Similar case may be a conditional closure.
+		if ( 'PHPCS_T_CLOSURE' === end( $this->tokens[ $stackPtr ]['conditions'] ) ) {
+			return false;
+		}
+
+		// Loop over the array of conditions and look for an IF.
+		reset( $this->tokens[ $stackPtr ]['conditions'] );
+
+		if ( true === array_key_exists( 'conditions', $this->tokens[ $stackPtr ] )
+			&& true === is_array( $this->tokens[ $stackPtr ]['conditions'] )
+			&& false === empty( $this->tokens[ $stackPtr ]['conditions'] )
+		) {
+			foreach ( $this->tokens[ $stackPtr ]['conditions'] as $tokenPtr => $tokenCode ) {
+				if ( T_IF === $this->tokens[ $stackPtr ]['conditions'][ $tokenPtr ] ) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * Is the token returning void
+	 *
+	 * @param int $stackPtr The position in the stack where the token was found.
+	 *
+	 * @return bool
+	 **/
+	private function isReturningVoid( $stackPtr ) {
+
+		$nextToReturnTokenPtr = $this->phpcsFile->findNext(
+			array( Tokens::$emptyTokens ), // types.
+			( $stackPtr + 1 ), // start.
+			null, // end.
+			true, // exclude.
+			null, // value.
+			false // local.
+		);
+
+		if ( T_SEMICOLON === $this->tokens[ $nextToReturnTokenPtr ]['code'] ) {
+			return true;
+		}
+
+		return false;
+	}
+}
diff --git a/WordPressVIPMinimum/Tests/Filters/AlwaysReturnUnitTest.inc b/WordPressVIPMinimum/Tests/Filters/AlwaysReturnUnitTest.inc
new file mode 100644
index 00000000..3fb5ce08
--- /dev/null
+++ b/WordPressVIPMinimum/Tests/Filters/AlwaysReturnUnitTest.inc
@@ -0,0 +1,103 @@
+<?php
+
+function good_example_function() {
+	if ( 1 === 0  ) {
+		if ( 1 === 1 ) {
+			return 'ahoj';
+		} else {
+			return 'hello';
+		}
+	}
+	return 'This is fine.';
+}
+add_filter( 'good_example_function_filter', 'good_example_function' );
+
+function bad_example_function() {
+	if ( 1 === 0  ) {
+		if ( 1 === 1 ) {
+			return 'ahoj';
+		} else {
+			return 'hello';
+		}
+	}
+	// Missing universal return.
+}
+add_filter( 'bad_example_function_filter', 'bad_example_function' );
+
+class good_example_class {
+	public function __construct() {
+		add_filter( 'good_example_class_filter', array( $this, 'class_filter' ) );
+	}
+
+	public function class_filter() {
+		if ( 1 === 1 ) {
+			if ( 1 === 0 ) {
+				return 'whoops';
+			} else {
+				return 'here!';
+			}
+		}
+		return 'This is Okay';
+	}
+}
+
+class bad_example_class {
+	public function __construct() {
+		add_filter( 'bad_example_class_filter', array( $this, 'class_filter' ) );
+	}
+
+	public function class_filter() {
+		if ( 1 === 1 ) {
+			if ( 1 === 0 ) {
+				return 'whoops';
+			} else {
+				return 'here!';
+			}
+		}
+		// Missing universal return.
+	}
+}
+
+if ( ! class_exists( 'another_good_example_class' ) ) {
+	class another_good_example_class {
+		public function __construct() {
+			add_filter( 'another_good_example_class_filter', array( $this, 'class_filter' ) );
+		}
+
+		public function class_filter() {
+			if ( 1 === 1 ) {
+				if ( 1 === 0 ) {
+					return 'whoops';
+				} else {
+					return 'here!';
+				}
+			}
+			return 'This is Okay';
+		}
+	}
+}
+
+add_filter( 'good_example_closure', function() {
+	if ( 1 === 0 ) {
+		return 'Hello';
+	} else {
+		return 'Hey';
+	}
+} );
+
+add_filter( 'bad_example_closure', function() {
+	if ( 1 === 0 ) {
+		return 'hey';
+	}
+	// Missing else return;
+} );
+
+add_filter( 'another_bad_example_closure', function() {
+	return;
+} );
+
+if ( 1 === 1 ) {
+	add_filter( 'another_good_example_closure', function () {
+		return 'hello';
+	} );
+}
\ No newline at end of file
diff --git a/WordPressVIPMinimum/Tests/Filters/AlwaysReturnUnitTest.php b/WordPressVIPMinimum/Tests/Filters/AlwaysReturnUnitTest.php
new file mode 100644
index 00000000..92638d36
--- /dev/null
+++ b/WordPressVIPMinimum/Tests/Filters/AlwaysReturnUnitTest.php
@@ -0,0 +1,41 @@
+<?php
+/**
+ * Unit test class for WordPressVIPMinimum Coding Standard.
+ *
+ * @package VIPCS\WordPressVIPMinimum
+ */
+
+namespace WordPressVIPMinimum\Tests\Filters;
+
+use PHP_CodeSniffer\Tests\Standards\AbstractSniffUnitTest;
+/**
+ * Unit test class for the Filters/AlwaysReturn sniff.
+ *
+ * @package VIPCS\WordPressVIPMinimum
+ */
+class AlwaysReturnUnitTest extends AbstractSniffUnitTest {
+
+	/**
+	 * Returns the lines where errors should occur.
+	 *
+	 * @return array <int line number> => <int number of errors>
+	 */
+	public function getErrorList() {
+		return array();
+	}
+
+	/**
+	 * Returns the lines where warnings should occur.
+	 *
+	 * @return array <int line number> => <int number of warnings>
+	 */
+	public function getWarningList() {
+		return array(
+			15 => 1,
+			49 => 1,
+			88 => 1,
+			95 => 1,
+		);
+	}
+
+} // End class.