how to make it mandatory to attach a file to create a task?

[Sergio Silva]

I need to create a task that is mandatory to attach a file.

[AlissonA]

You can create in a validator in your workflow so that when you create a issue, the attachment field is required.

In the field to add a Validator, you should add the 'Fields Required' option, and then in the next page, select all the fields you would like to be required in this workflow.

You can see more information in how to add a validator in the following link - http://confluence.atlassian.com/display/JIRA/Configuring+Workflow#ConfiguringWorkflow-ApplyingValidatorstoTransitions