Can not delete this order as an invoice has been applied to this order
Sage 50 is blocking deletion of a sales order because an invoice is linked to it and must be dealt with first.
Sage 50 is telling you, in plain terms, that the sales order you are trying to delete has already been at least partially fulfilled — an invoice has been generated from it, and that invoice is still in your data. The order and the invoice are linked, and Sage 50 will not let you remove one side of that link while the other side still exists.
What the message actually means
The wording “Can not delete this order as an invoice has been applied to this order” sounds like a permanent lock, but it is really a sequencing rule. Sage 50 needs you to deal with the invoice first, then come back to the order. The order itself is not necessarily untouchable — it just cannot be the first thing you delete.
Delete or void the linked invoice first
The safest approach is to locate the invoice that was created from this order. Once you delete or void that invoice (depending on whether it has been posted and whether your version allows voiding), the link to the order is broken and the order can then be deleted normally. If you are not sure which invoice is linked, check the order’s history or linked-transaction tab — the exact steps depend on your version of Sage 50.
Check whether the order is fully invoiced
Sometimes an order reaches a state where every line has been invoiced and the order is effectively closed but still visible. In that situation there may be nothing left to delete — the order is simply complete. Reviewing the order’s status before attempting deletion can save unnecessary work.
When the data will not cooperate
If the invoice has already been deleted but Sage 50 still blocks the order, or if the order and invoice appear out of sync, the underlying links in the database may be damaged. This is the point where the file likely needs professional attention rather than continued manual troubleshooting. Our engineers regularly work on Sage 50 / Peachtree / Simply Accounting databases where transaction links have become inconsistent, and we can evaluate the file to determine what is recoverable. If you are also considering moving away from Sage 50 entirely, we offer a Sage 50 to QuickBooks conversion service that may be relevant.
If the order will not delete even after the linked invoice is gone, send us the file for a free evaluation — we will tell you what is wrong and what it takes to fix it before any work begins.