1.Where, based on a simplified uncertainty assessment, the use of measurement systems outside the operator’s own control, compared to the use of those within the operator’s own control pursuant to Article 28, allows the operator to comply with at least as high a tier, gives more reliable results and is less prone to control risks, the operator shall determine the activity data from measurement systems outside its own control.
To that end, the operator may revert to one of the following data sources:
(a)amounts from invoices issued by a trade partner, provided that a commercial transaction between two independent trade partners takes place;
(b)direct readings from the measurement systems.
2.The operator shall ensure compliance with the applicable tier pursuant to Article 26.
To that end, the maximum permissible error in service allowed by relevant legislation for national legal metrological control for the relevant commercial transaction may be used as uncertainty without providing further evidence.
Where the applicable requirements under national legal metrological control are less stringent than the applicable tier pursuant to Article 26, the operator shall obtain evidence on the applicable uncertainty from the trade partner responsible for the measurement system.