How to fix Xero error "Payments can only be made against authorized documents" in Peakflo

In Xero, you can only proceed with payments against a bill that is in the Authorized state.
Additionally, the error could be due to synchronization issues. Let's say you're adding a payment against a bill manually in Xero. The bill will change to the Paid status in Xero, but in Peakflo the bill is still in the Scheduled tab. Xero rejects the payment as it won't allow the payment to be applied to the Paid bill.

In Xero, remove the payment associated with the bill.
In Peakflo, go to the Accounting section and find the bill with the sync error (you can sort by dates to navigate easier). Then, re-sync the bill.
Xero syncs with Peakflo in 15 intervals. For now, sit tight, grab some snacks, and check back 30 minutes later to see the changes reflected.
For more info, please check our Xero support documentation.