You can change a tronc batch, depending on his status. There are three statuses for tronc batches:
Open: You can amend this before submitting to payroll.
Submitted to Payroll: Batches that are submitted to payroll cannot be edited and are sat awaiting an export to payroll.
Sent to Payroll: Batches that you've sent to payroll cannot be edited and this status means they've already been exported to the payroll system.