Welcome to the Community, @fernandobartolom.
You can use TAGS even on the Simple Start plan. You can enable that feature via QuickBooks Labs.
To turn it on:
You can now go to Settings ⚙ and under Lists, Tags should be available.
You can use these articles to get started with tags:
To know more about QuickBooks Online and its features per plan - here's the QBSE, QBO comparison chart.
If you have other questions, feel free to drop a comment and I'd be glad to help.