Hi Fernando,
When Azure SQL Managed Instance is Stopped, you are only charged for storage. Excerpt from documentation:
Stopped instances don't get billed for vCores and the SQL license, they're charged only for data and backup storage. However, vCores and license billing is charged for every started hour. For example, at 12:01, you're charged for the entire hour, even if the instance is stopped within the hour.
Azure SQL Managed Instance pricing page has pricing details for storage:
https://azure.microsoft.com/en-us/pricing/details/azure-sql-managed-instance/single/
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP