diff --git a/scripts/changelog.sh b/scripts/changelog.sh
index af986ed..b58f0b3 100755
--- a/scripts/changelog.sh
+++ b/scripts/changelog.sh
@@ -4,6 +4,11 @@ set -euo pipefail
 source "$(dirname $0)/utils.sh"
 goto_root
 
+## Check parameters and environment variables
+# PARAMETER: The next version to release (i.e. v3.0.0)
+# JIRA_API_TOKEN: the user api token to login jira
+# JIRA_LOGIN: the user email to login on jira
+
 if [ $# -eq 0 ]; then
     echo "Target tag is required as parameter"
     exit 1
@@ -31,30 +36,38 @@ SAVEIFS=$IFS
 IFS=$(echo -en "\n\b")
 TMP=$(mktemp -d)
 
+# Clean when exit
 err() {
     rm -fr ${TMP}
     IFS=$SAVEIFS
 }
 trap 'err $LINENO' ERR TERM EXIT INT
 
+# Create the go-jira template with issue, status and summary as CSV
 mkdir -p ${HOME}/.jira.d/templates
 cat > ${HOME}/.jira.d/templates/changelog <<EOF
 {{ .fields.issuetype.name }};{{ .key }};{{if .fields.status -}}{{ .fields.status.name }}{{end -}};{{ .fields.summary }}
 EOF
 
+# List all issues in commits from previous tag
 TMP_ISSUES=$TMP/issues.txt
 for commit in $(git log $(git describe --tags --abbrev=0)..HEAD --oneline); do
     [[ $commit =~ ^.*(MON-[0-9]+).*$ ]] && echo "${BASH_REMATCH[1]}"
 done | sort -u > $TMP_ISSUES
 
 TMP_CHANGELOG=${TMP}/changelog.md
+# init changelog for next version
 echo -e "\n# $TAG_TARGET ($(LANG=eng date +"%B %d, %Y"))" >> $TMP_CHANGELOG
 for issue in $(cat $TMP_ISSUES); do
+    # retrieve jira information from go-jira template
     IFS=';' read -r type issue status summary < <(jira --endpoint=${JIRA_ENDPOINT} --login=${JIRA_LOGIN} view $issue --template=changelog)
+    # Ignore if issue is not in required status
     if [[ "$JIRA_STATUS" == *"$status"* ]]; then
+        # add line for type only once
         if ! grep -q "^## $type" $TMP_CHANGELOG; then 
             echo -e "\n## $type\n" >> $TMP_CHANGELOG
         fi
+        # add jira issue line to changelog
         echo "*   [[$issue](${JIRA_ENDPOINT}/browse/${issue})] - $summary" >> $TMP_CHANGELOG
     else
         echo "Ignore $issue with status \"$status\" not in [$JIRA_STATUS] ($summary)"
@@ -62,8 +75,17 @@ for issue in $(cat $TMP_ISSUES); do
 done
 
 cat $TMP_CHANGELOG
-read -p 'Add this to CHANGELOG.md ? (y/n): ' -r answer
+# Ask for confirmation to update changelog
+read -p 'Update CHANGELOG.md with this ? (y/n): ' -r answer
 if [[ "$answer" == "y" ]]; then
-    echo -e "$(cat $TMP_CHANGELOG)\n$(cat CHANGELOG.md)" > CHANGELOG.md
+    separator='\n'
+    # Remove target tag changelog if already exist
+    if grep -q $TAG_TARGET CHANGELOG.md; then
+        prev_tag=$(grep '^# v' CHANGELOG.md | sed -n 2p)
+        sed -i "/${prev_tag}/,\$!d" CHANGELOG.md
+        separator="${separator}\n"
+    fi
+    # Add target tag changelog to final changelog
+    echo -e "$(cat $TMP_CHANGELOG)${separator}$(cat CHANGELOG.md)" > CHANGELOG.md
 fi