In the template anatomy, you cant set stack-level tags directly. However you can create a wrapper template, having a single resource of AWS::CloudFormation::Stack.
You can define stack-level tags on that resource:
{
"AWSTemplateFormatVersion": "2010-09-09",
"Description": "WrapperTemplate",
"Resources": {
"WrappedStackWithStackLevelTags": {
"Type" : "AWS::CloudFormation::Stack",
"Properties" : {
"Tags" : [ { "Key" : "Stage", "Value" : "QA" } ],
"TemplateURL" : "your-original-template-s3-url"
}
}
}
}