An admin user can delete transactions by navigating to Config > Transactions, and selecting the Delete unreconciled transactions or the Delete reconciled transactions tab.
On the 'Delete unreconciled transactions' tab, you can delete transactions that have been imported, but have not been matched to a trading partner or to all required dimension items.
On the 'Delete reconciled transactions' tab, you can delete transactions that have been matched to a trading partner and all required dimension items. There are several available filters to narrow down which transactions to delete.
For more information about these two tabs, check out our dedicated help center article on deleting transactions.