Occasionally invoices don't show a trash can or edit button. This is because Xero is not allowing a deletion to the invoice. There are two possible reasons for this.
Reason 1 - Payments
If you are using Xero and there is a payment applied to the invoice, you can't edit or delete the invoice (this is a Xero rule). In a case like this, you would need to remove the payments from the invoice first so that you can edit or delete the invoice.
NOTE *** You should speak with your financial advisor about this first. Depending on when the payments were recorded, it may not be advisable to edit or delete them.
Reason 2 - Lock Period
The other reason that invoices may not be editable is that they are in a lock period as defined in your accounting settings in Xero. Again, you should speak to your financial advisor about editing items that are in a lock period.
See this Xero article for more details on Lock Dates CLICK HERE.