An invoice failed to post to the accounting system, and was manually processed on the accounting system. Should I post this invoice from Varibill to the accounting system?

Once you have generated an invoice in your accounting system that was also produced by Varibill, we do not recommend that you post the Varibill invoice to your accounting system as this will create duplicate entries in your General Ledger and Customer Ledger. If you credit the manual invoice raised in your accounting system you are welcome to post the Varibill invoice to your accounting system. 

Read more on docs.varibill.com for more information on posting invoices to your accounting system and reprocessing a failed invoice.