In the context of a Supplier, 'Invoicing Tolerance' is the percentage value above or below the value of their PO that the Supplier can charge.
When the Supplier's invoice is received by the system, any variance between the PO value and the invoice value is automatically added to the Project as an 'Extra' to ensure the costs balance exactly.
The percentage tolerance is usually small and is primarily used to enable the Supplier to invoice allowing for rounding differences (particularly relevant where there is a high volume of invoicing).
An 'Invoicing Tolerance' of 0% would ensure that the Supplier is only ever able to submit their invoice for a value identical to the PO. If the Supplier wished to submit a different value they would have to submit a manual invoice in the traditional manner.