When you generate invoices from daysheets, Abio tracks back to each reimbursable on each daysheet to see if there are supporting documents to include on the invoice.
Wherever appropriate, Abio allows you to upload documents to support invoicing. For example, this receipt has been uploaded to support this materials purchase:

Every supporting document can be included with the generated invoice by entering ‘Y’ in the billing setup, include with invoice? field:

If a daysheet bills this materials purchase, the invoice generated will include the receipt in the invoice PDF. The invoice PDF will start with the invoice, then the daysheets, then the supporting documents in the order specified on the document.
If this invoice was initiated by a purchase order that also includes supporting documents, those supporting documents can also be included.
Purchase orders can be received, in which case packing slips and receipts might be stored with the receiving entry.
Purchase orders might be generated from Requisitions and RFQs. In some cases, clients ask that materials not be purchased without their signoff on the requisitions. Those signed documents can be stored with the requisition, and pulled up on the invoice because there’s a trail from the invoice to the purchase order to the requisition.
In addition to requisition documents, quotes and purchase orders can be attached to the job’s area. Each area can be associated with change orders, and the change orders can be stored as supporting documents on the job’s area. These too can be included in the invoice.
When Abio generates the invoice for selected daysheets, the supporting documents it gathers from the component items are listed on the Supporting Documents tab:

You can preview the invoice PDF that will be emailed to the customer on the Preview tab:
