TAX Invoice Tax Amount Tolerance Setting

[MarkLi1]

TAX Invoice Tolerance Setting Solution (Business Logic)
1. Background and Reiteration of Requirements
In the Concur to SAP system integration project, the finance department faces a core
challenge: how to intelligently handle discrepancies in GST (Goods and Services Tax)
amounts on supplier invoices. The specific requirements are:
Allow: For invoices with a large number of line items (e.g., 200 lines), small
discrepancies (e.g., an accumulation of 0.01 difference per line, potentially totaling
up to 2.00) due to rounding of each line's GST calculation or other rounding rules
(e.g., round up, round down). Such discrepancies are considered reasonable and
should be allowed for posting.
Block: For manually issued single-line invoices, if a similar discrepancy of 2.00
occurs, it is considered an unreasonable calculation error and should be blocked
from posting, requiring the supplier to provide a new invoice.
The key is to design a tolerance rule that can differentiate between these two scenarios,
rather than simply setting a fixed amount or percentage tolerance.

What is the best practice for this kind of requirement in your project?