When attempting to delete SKUs with associated activity such as Purchase Orders (POs) or FBA Shipments, the system will display an error indicating the presence of activity on the SKU. To proceed with the deletion, it is necessary to first remove all the related POs or other associated activities linked to the item. Once these activities have been deleted, the SKU can then be removed. However, it is generally not recommended to perform this action as it can disrupt the integrity of your data within the software.