diff --git a/src/Liip/RMT/Action/BaseAction.php b/src/Liip/RMT/Action/BaseAction.php
index 502cb41c..0a365ddb 100644
--- a/src/Liip/RMT/Action/BaseAction.php
+++ b/src/Liip/RMT/Action/BaseAction.php
@@ -51,6 +51,20 @@ public function getInformationRequests()
         return array();
     }
 
+    /**
+     * This method is called after all registered information collectors have
+     * been called to validate that the action has all necessary information
+     * if anything is missing an exception should be thrown.
+     * When called, the 'current-version' and 'new-version' parameters are
+     * already known, so a check can be made on those.
+     *
+     * @throws \Exception
+     */
+    public function validateContext()
+    {
+
+    }
+
     /**
      * A common method to confirm success to the user
      */
diff --git a/src/Liip/RMT/Action/VcsTagAction.php b/src/Liip/RMT/Action/VcsTagAction.php
index ecff5aa5..8ab9082a 100644
--- a/src/Liip/RMT/Action/VcsTagAction.php
+++ b/src/Liip/RMT/Action/VcsTagAction.php
@@ -20,11 +20,20 @@ class VcsTagAction extends BaseAction
 {
     public function execute()
     {
-        Context::get('vcs')->createTag(
-            Context::get('vcs')->getTagFromVersion(
-                Context::getParam('new-version')
-            )
-        );
+        Context::get('vcs')->createTag($this->getVersion());
         $this->confirmSuccess();
     }
+
+    protected function getVersion()
+    {
+        return Context::get('vcs')->getTagFromVersion(
+            Context::getParam('new-version')
+        );
+    }
+
+    public function validateContext()
+    {
+        parent::validateContext();
+        Context::get('vcs')->validateTag($this->getVersion());
+    }
 }
diff --git a/src/Liip/RMT/Command/ReleaseCommand.php b/src/Liip/RMT/Command/ReleaseCommand.php
index c799ba94..a5c5f5be 100644
--- a/src/Liip/RMT/Command/ReleaseCommand.php
+++ b/src/Liip/RMT/Command/ReleaseCommand.php
@@ -136,13 +136,20 @@ protected function execute(InputInterface $input, OutputInterface $output)
         );
         Context::getInstance()->setParameter('new-version', $newVersion);
 
+        foreach (array('prerequisites', 'pre-release-actions', 'post-release-actions') as $listName) {
+            foreach(Context::getInstance()->getList($listName) as $action) {
+                $action->validateContext();
+            }
+        }
+        Context::get('version-persister')->validateContext();
+
         $this->executeActionListIfExist('pre-release-actions');
 
         $this->getOutput()->writeSmallTitle('Release process');
         $this->getOutput()->indent();
 
         $this->getOutput()->writeln("A new version named [<yellow>$newVersion</yellow>] is going to be released");
-        Context::get('version-persister')->save($newVersion);
+        Context::get('version-persister')->save();
         $this->getOutput()->writeln('Release: <green>Success</green>');
 
         $this->getOutput()->unIndent();
diff --git a/src/Liip/RMT/Exception/InvalidTagNameException.php b/src/Liip/RMT/Exception/InvalidTagNameException.php
new file mode 100644
index 00000000..30d59dbe
--- /dev/null
+++ b/src/Liip/RMT/Exception/InvalidTagNameException.php
@@ -0,0 +1,18 @@
+<?php
+
+/*
+ * This file is part of the project RMT
+ *
+ * Copyright (c) 2013, Liip AG, http://www.liip.ch
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Liip\RMT\Exception;
+
+use Liip\RMT\Exception as BaseException;
+
+class InvalidTagNameException extends BaseException
+{
+}
diff --git a/src/Liip/RMT/Exception/TagAlreadyExistsException.php b/src/Liip/RMT/Exception/TagAlreadyExistsException.php
new file mode 100644
index 00000000..7a43ecc6
--- /dev/null
+++ b/src/Liip/RMT/Exception/TagAlreadyExistsException.php
@@ -0,0 +1,18 @@
+<?php
+
+/*
+ * This file is part of the project RMT
+ *
+ * Copyright (c) 2013, Liip AG, http://www.liip.ch
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Liip\RMT\Exception;
+
+use Liip\RMT\Exception as BaseException;
+
+class TagAlreadyExistsException extends BaseException
+{
+}
diff --git a/src/Liip/RMT/VCS/Git.php b/src/Liip/RMT/VCS/Git.php
index 4c35efb0..6950be0f 100644
--- a/src/Liip/RMT/VCS/Git.php
+++ b/src/Liip/RMT/VCS/Git.php
@@ -11,6 +11,10 @@
 
 namespace Liip\RMT\VCS;
 
+use Liip\RMT\Exception;
+use Liip\RMT\Exception\InvalidTagNameException;
+use Liip\RMT\Exception\TagAlreadyExistsException;
+
 class Git extends BaseVCS
 {
     protected $dryRun = false;
@@ -45,6 +49,19 @@ public function getTags()
         return $this->executeGitCommand('tag');
     }
 
+    public function validateTag($tagName)
+    {
+        try {
+            $this->executeGitCommand("check-ref-format --allow-onelevel $tagName");
+        } catch(Exception $e) {
+            throw new InvalidTagNameException("'$tagName' is an invalid tag name for git.");
+        }
+
+        if(in_array($tagName, $this->getTags())) {
+            throw new TagAlreadyExistsException("'$tagName' already exists.");
+        }
+    }
+
     public function createTag($tagName)
     {
         return $this->executeGitCommand("tag $tagName");
@@ -79,6 +96,11 @@ public function getCurrentBranch()
         throw new \Liip\RMT\Exception('Not currently on any branch');
     }
 
+    /**
+     * @param $cmd
+     * @throws \Liip\RMT\Exception
+     * @return string[]
+     */
     protected function executeGitCommand($cmd)
     {
         // Avoid using some commands in dry mode
@@ -86,7 +108,7 @@ protected function executeGitCommand($cmd)
             if ($cmd !== 'tag') {
                 $cmdWords = explode(' ', $cmd);
                 if (in_array($cmdWords[0], array('tag', 'push', 'add', 'commit'))) {
-                    return;
+                    return [];
                 }
             }
         }
@@ -95,7 +117,7 @@ protected function executeGitCommand($cmd)
         $cmd = 'git ' . $cmd;
         exec($cmd, $result, $exitCode);
         if ($exitCode !== 0) {
-            throw new \Liip\RMT\Exception('Error while executing git command: ' . $cmd . "\n" . implode("\n", $result));
+            throw new Exception('Error while executing git command: ' . $cmd . "\n" . implode("\n", $result));
         }
 
         return $result;
diff --git a/src/Liip/RMT/VCS/Hg.php b/src/Liip/RMT/VCS/Hg.php
index 1fa713fc..1510a1aa 100644
--- a/src/Liip/RMT/VCS/Hg.php
+++ b/src/Liip/RMT/VCS/Hg.php
@@ -11,6 +11,9 @@
 
 namespace Liip\RMT\VCS;
 
+use Liip\RMT\Exception\InvalidTagNameException;
+use Liip\RMT\Exception\TagAlreadyExistsException;
+
 class Hg extends BaseVCS
 {
     protected $dryRun = false;
@@ -53,6 +56,17 @@ public function getTags()
         return $tags;
     }
 
+    public function validateTag($tagName)
+    {
+        if(preg_match("/[:\r\n]/", $tagName) > 0 || preg_match("/^[0-9]*$/", $tagName) > 0) {
+            throw new InvalidTagNameException("'$tagName' is an invalid tag name for mercurial.");
+        }
+
+        if(in_array($tagName, $this->getTags())) {
+            throw new TagAlreadyExistsException("'$tagName' already exists.");
+        }
+    }
+
     public function createTag($tagName)
     {
         return $this->executeHgCommand("tag $tagName");
diff --git a/src/Liip/RMT/VCS/VCSInterface.php b/src/Liip/RMT/VCS/VCSInterface.php
index a6a858e1..da1f725b 100644
--- a/src/Liip/RMT/VCS/VCSInterface.php
+++ b/src/Liip/RMT/VCS/VCSInterface.php
@@ -11,6 +11,9 @@
 
 namespace Liip\RMT\VCS;
 
+use Liip\RMT\Exception\InvalidTagNameException;
+use Liip\RMT\Exception\TagAlreadyExistsException;
+
 interface VCSInterface
 {
     /**
@@ -25,6 +28,17 @@ public function getCurrentBranch();
      */
     public function getTags();
 
+    /**
+     * Validate that a tag name is valid for the given VCS. If possible
+     * should also check if this tag already exists or if we can create
+     * it freely.
+     *
+     * @param $tagName
+     * @throws InvalidTagNameException in case the name is invalid
+     * @throws TagAlreadyExistsException in case the tag name already exists
+     */
+    public function validateTag($tagName);
+
     /**
      * Create a new tag at the current position
      *
diff --git a/src/Liip/RMT/Version/Persister/ChangelogPersister.php b/src/Liip/RMT/Version/Persister/ChangelogPersister.php
index e1140128..cb63bd3a 100644
--- a/src/Liip/RMT/Version/Persister/ChangelogPersister.php
+++ b/src/Liip/RMT/Version/Persister/ChangelogPersister.php
@@ -42,11 +42,11 @@ public function getCurrentVersion()
         return $this->changelogManager->getCurrentVersion();
     }
 
-    public function save($versionNumber)
+    public function save()
     {
         $comment = Context::get('information-collector')->getValueFor('comment');
         $type = Context::get('information-collector')->getValueFor('type', null);
-        $this->changelogManager->update($versionNumber, $comment, array('type' => $type));
+        $this->changelogManager->update(Context::getParam('new-version'), $comment, array('type' => $type));
     }
 
     public function getInformationRequests()
@@ -54,6 +54,11 @@ public function getInformationRequests()
         return array('comment');
     }
 
+    public function validateContext()
+    {
+
+    }
+
     public function init()
     {
         // TODO: Implement init() method.
diff --git a/src/Liip/RMT/Version/Persister/PersisterInterface.php b/src/Liip/RMT/Version/Persister/PersisterInterface.php
index 95940c8f..598b7acb 100644
--- a/src/Liip/RMT/Version/Persister/PersisterInterface.php
+++ b/src/Liip/RMT/Version/Persister/PersisterInterface.php
@@ -26,10 +26,12 @@ public function __construct($options = array());
      */
     public function getCurrentVersion();
 
-    public function save($versionNumber);
+    public function save();
 
     public function getInformationRequests();
 
+    public function validateContext();
+
     // Use the very first time to init this persistence
     public function init();
 }
diff --git a/src/Liip/RMT/Version/Persister/VcsTagPersister.php b/src/Liip/RMT/Version/Persister/VcsTagPersister.php
index b6af61f8..82431b31 100644
--- a/src/Liip/RMT/Version/Persister/VcsTagPersister.php
+++ b/src/Liip/RMT/Version/Persister/VcsTagPersister.php
@@ -46,13 +46,23 @@ public function getCurrentVersion()
         return array_pop($versions);
     }
 
-    public function save($versionNumber)
+    public function getNewVersion()
     {
-        $tagName = $this->getTagFromVersion($versionNumber);
+        return $this->getTagFromVersion(Context::getParam('new-version'));
+    }
+
+    public function save()
+    {
+        $tagName = $this->getNewVersion();
         Context::get('output')->writeln("Creation of a new VCS tag [<yellow>$tagName</yellow>]");
         $this->vcs->createTag($tagName);
     }
 
+    public function validateContext()
+    {
+        Context::get('vcs')->validateTag($this->getNewVersion());
+    }
+
     public function init()
     {
     }
diff --git a/test/Liip/RMT/Tests/Functional/HgTest.php b/test/Liip/RMT/Tests/Functional/HgTest.php
index ad6b6459..ddd68301 100644
--- a/test/Liip/RMT/Tests/Functional/HgTest.php
+++ b/test/Liip/RMT/Tests/Functional/HgTest.php
@@ -22,13 +22,21 @@ public static function cleanTags($tags)
         }, $tags);
     }
 
-    public function testInitialVersion()
+    public function testNoSimpleGenerator()
     {
         $this->initHg();
         $this->createConfig('simple', 'vcs-tag', array('vcs' => 'hg'));
+        exec('./RMT release -n --confirm-first 2> /dev/null', $result, $code);
+        $this->assertEquals($code, 1);
+    }
+
+    public function testInitialVersion()
+    {
+        $this->initHg();
+        $this->createConfig('simple', array('name' => 'vcs-tag', 'tag-prefix' => 'v'), array('vcs' => 'hg'));
         exec('./RMT release -n --confirm-first');
         exec('hg tags', $tags);
-        $this->assertEquals(array('tip', '1'), static::cleanTags($tags));
+        $this->assertEquals(array('tip', 'v1'), static::cleanTags($tags));
     }
 
     public function testInitialVersionSemantic()
@@ -43,13 +51,13 @@ public function testInitialVersionSemantic()
     public function testSimple()
     {
         $this->initHg();
-        exec('hg tag 1');
-        exec('hg tag 3');
+        exec('hg tag v1');
+        exec('hg tag v3');
         exec('hg tag toto');
-        $this->createConfig('simple', 'vcs-tag', array('vcs' => 'hg'));
+        $this->createConfig('simple', array('name' => 'vcs-tag', 'tag-prefix' => 'v'), array('vcs' => 'hg'));
         exec('./RMT release -n');
         exec('hg tags', $tags);
-        $this->assertEquals(array('tip', '4', 'toto', '3', '1'), static::cleanTags($tags));
+        $this->assertEquals(array('tip', 'v4', 'toto', 'v3', 'v1'), static::cleanTags($tags));
     }
 
     public function testSemantic()
@@ -65,12 +73,12 @@ public function testSemantic()
     public function testTagPrefix()
     {
         $this->initHg();
-        exec('hg tag 2');
+        exec('hg tag v2');
         exec('hg tag v_1');
         $this->createConfig('simple', array('name' => 'vcs-tag', 'tag-prefix' => 'v_'), array('vcs' => 'hg'));
         exec('./RMT release -n');
         exec('hg tags', $tags);
-        $this->assertEquals(array('tip', 'v_2', 'v_1', '2'), static::cleanTags($tags));
+        $this->assertEquals(array('tip', 'v_2', 'v_1', 'v2'), static::cleanTags($tags));
     }
 
     public function testTagPrefixWithBranchNamePlaceHolder()
diff --git a/test/Liip/RMT/Tests/Unit/VCS/GitTest.php b/test/Liip/RMT/Tests/Unit/VCS/GitTest.php
index f96a938c..56ff64e5 100644
--- a/test/Liip/RMT/Tests/Unit/VCS/GitTest.php
+++ b/test/Liip/RMT/Tests/Unit/VCS/GitTest.php
@@ -60,6 +60,53 @@ public function testGetTags()
         $this->assertEquals(array('1.0.0', '1.1.0'), $vcs->getTags());
     }
 
+    /**
+     * @dataProvider invalidTagNames
+     * @expectedException \Liip\RMT\Exception\InvalidTagNameException
+     */
+    public function testInvalidateTag($tag)
+    {
+        $vcs = new Git();
+        $vcs->validateTag($tag);
+    }
+
+    public function invalidTagNames()
+    {
+        return array(
+            array("test..test"),
+            array("test*test"),
+            array('test[test'),
+            array("test?test"),
+            array("test\ntest"),
+            array("test\rtest"),
+            array("test."),
+            array("@"),
+            array("\\"),
+        );
+    }
+
+    /**
+     * @dataProvider validTagNames
+     */
+    public function testValidateTag($tag)
+    {
+        $vcs = new Git();
+        $vcs->validateTag($tag);
+    }
+
+    public function validTagNames()
+    {
+        return array(
+            array('test/test'),
+            array('test'),
+            array(2345),
+            array('1.2'),
+            array('1.2.3'),
+            array('v1.2'),
+            array('v1.2.3'),
+        );
+    }
+
     public function testCreateTag()
     {
         $vcs = new Git();
diff --git a/test/Liip/RMT/Tests/Unit/VCS/HgTest.php b/test/Liip/RMT/Tests/Unit/VCS/HgTest.php
index beef3c7a..0e9a4bf5 100644
--- a/test/Liip/RMT/Tests/Unit/VCS/HgTest.php
+++ b/test/Liip/RMT/Tests/Unit/VCS/HgTest.php
@@ -60,6 +60,47 @@ public function testGetTags()
         $this->assertEquals(array('tip', '1.1.0', '1.0.0'), $vcs->getTags());
     }
 
+    /**
+     * @dataProvider invalidTagNames
+     * @expectedException \Liip\RMT\Exception\InvalidTagNameException
+     */
+    public function testInvalidateTag($tag)
+    {
+        $vcs = new Hg();
+        $vcs->validateTag($tag);
+    }
+
+    public function invalidTagNames()
+    {
+        return array(
+            array(2345),
+            array('test:test'),
+            array("test\ntest"),
+            array("test\rtest"),
+        );
+    }
+
+    /**
+     * @dataProvider validTagNames
+     */
+    public function testValidateTag($tag)
+    {
+        $vcs = new Hg();
+        $vcs->validateTag($tag);
+    }
+
+    public function validTagNames()
+    {
+        return array(
+            array('test/test'),
+            array('test'),
+            array('1.2'),
+            array('1.2.3'),
+            array('v1.2'),
+            array('v1.2.3'),
+        );
+    }
+
     public function testCreateTag()
     {
         $vcs = new Hg();