TeamCity does not have a build-in feature to tag a build in a build stept but there is a workaroud for that -> using REST API https://teamcity-support.jetbrains.com/hc/en-us/community/posts/206830245-Add-build-tag-from-a-build-step.

• $1 - server url
• $2 - password (special characters makes it to fail)
• $3 - build Id (if tweaked then can be used other TC build locator)
• $4 - tag name

• from CMD:

"C:\Program Files\Git\bin\sh.exe" -c "myPath/tagTCbuild.sh teamcity.mydomain.com mypassword %teamcity.build.id% 'myTag'"

• from Powershell:

& "C:\Program Files\Git\bin\sh.exe" -c "myPath/tagTCbuild.sh teamcity.mydomain.com mypassword %teamcity.build.id% 'myTag'"