What could be the reason for error "Some of the bill lines differ from the corresponding lines of the related purchase order. For details, review warnings in the lines."

The part that stands out is the Unbilled Qty and Unbilled Amount both being 0. That usually means Acumatica already considers that PO line fully billed.

I’d check whether there are any other released or unreleased AP documents tied to that PO/receipt line. Even if the quantities, cost, and amounts all match, Acumatica can still throw this warning if it thinks there is no remaining balance left to bill.

If there aren’t any other AP documents against it, then I’d start looking at whether the PO/AP billing linkage somehow got out of sync.

Elijah's got it — the zeros are the tell.

To find what already billed that line, two spots worth checking: the PO History tab on PO301000 (receipts on the left, AP documents on the right), and Purchase Order Receipt and Billing History (PO643000) off the PO's More menu. Between them you'll see every AP document sitting against that PO, released or not.

One setting worth knowing too: PO101000, General tab, Three-Way Match Validation → Bill Against Commitments. That's the switch for validating AP bill lines against POs, so it's useful to know how yours is set.

​@smilner3 ,Thanks for the response. There were no other bills created for this.  Three-Way Match Validation is set to as Validate with Warning. 

Michelle,

I built your scenario in a 2026 R1 instance to check this.

Completing a line doesn't touch the unbilled balance. I completed a line short with nothing billed against it and checked the row: Completed ticked, Closed clear, Billed Qty. 0.00, and the full amount still sitting in Unbilled Qty. and Unbilled Amount. That's by design. Completed only blocks the line from new receipts. The line stays billable, so the unbilled columns keep their value.

Your zeros point to something else, and it's visible on the line. Open the PO on PO301000, Document Details tab, and scroll right to the flag and billing columns: Completed, Canceled, Closed, Billed Qty., Billed Amount, Unbilled Qty., Unbilled Amount. Two things matter on that row:

• Closed ticked. The system sets Closed when it considers a line fully received and billed, and a closed line is excluded from receipts and AP bills entirely. That flag, not Completed, matches what you're describing.
• A value in Billed Qty. or Billed Amount. Then an AP document consumed the line, whether or not anyone remembers creating one.

Either way the fix is the same. More > Reopen Order drops the PO back to On Hold, editable, and all three flags can be cleared from there. Expect it to run back through approvals if you have an approval map on POs.

If the row shows neither, post two screenshots and I'll take a look: the Document Details row scrolled to those columns, and the PO History tab. Receipts on the left, AP documents on the right, and between them the trail usually shows what happened.