It depends on how the Workflow for the project is set up. There is a control that can be put on the workflow that will not allow you to close a Story or Task when the Sub-Tasks have not been marked Resolved.
I agree with Kathy. It has always been best practice to not close a parent ticket until the child tickets are resolved. If the child ticket is not resolved, then the parent ticket is not resolved either.
Conversely, I believe there is a Post-Function that can be set up on a Workflow to resolve all children if you resolve the Story.
But that also has its downside.
@Charlie_Vinall Welcome, welcome! Looks like you're already getting some great assistance. 😄 In the future, you can definitely post product-specific questions in our dedicated collections (just means you can get the absolute best answers to your questions). Be sure to check out off-topic threads like Friday Fun as well.