The audit authority shall establish the method for the selection of the sample (‘the sampling method’) in accordance with the requirements set out in this Article taking into account the internationally accepted auditing standards, INTOSAI, IFAC or IIA.

In addition to the explanations provided in the audit strategy, the audit authority shall keep a record of the documentation and professional judgement used to establish the sampling methods, covering the planning, selection, testing and evaluation stages, in order to demonstrate that the established method is suitable.

A sample shall be representative of the population from which it is selected and enable the audit authority to draw up a valid audit opinion in accordance with Article 127(5)(a) of Regulation (EU) No 1303/2013. That population shall comprise the expenditure of an operational programme or group of operational programmes covered by a common management and control system, which is included in the payment applications submitted to the Commission in accordance with Article 131 of Regulation (EU) No 1303/2013 for a given accounting year. The sample may be selected during or after the accounting year.

For the purpose of application of Article 127(1) of Regulation (EU) No 1303/2013, a sampling method is statistical when it ensures:

1. (i)

   a random selection of the sample items;

2. (ii)

   the use of probability theory to evaluate sample results, including measurement and control of the sampling risk and of the planned and achieved precision.

The sampling method shall ensure a random selection of each sampling unit in the population by using random numbers generated for each population unit in order to select the units constituting the sample or through systematic selection by using a random starting point and applying a systematic rule to select the additional items.

The sampling unit shall be determined by the audit authority, based on professional judgement. The sampling unit may be an operation, a project within an operation or a payment claim by a beneficiary. Information on the type of sampling unit determined and on the professional judgement used for that purpose shall be included in the control report.

Where the total expenditure relating to a sampling unit for the accounting year is a negative amount it shall be excluded from the population referred to in paragraph 3 above and shall be audited separately. The audit authority may also draw a sample of this separate population.

Where conditions for the proportional control provided for in Article 148(1) of Regulation (EU) No 1303/2013 apply, the audit authority may either exclude the items referred to in that Article from the population to be sampled or maintain the items in the population to be sampled and replace them if selected. The decision to use either exclusion or replacement of sampling units should be taken by the audit authority based on its professional judgement.

All expenditure declared to the Commission in the sample shall be subject to audit.

F2However, depending on the characteristics of sampling unit, the audit authority may decide to apply sub-sampling. The methodology for selection of the sub-sampling units shall follow the principles allowing projection at the level of the sampling unit.

The audit authority may stratify a population by dividing a population into sub-populations, each of which is a group of sampling units which have similar characteristics, in particular in terms of risk or expected error rate or where the population includes operations consisting of financial contributions from an operational programme to financial instruments or other high-value items.

The audit authority shall evaluate the reliability of the system as high, average or low, taking into account the results of systems audits to determine the technical parameters of sampling so that the combined level of assurance obtained from the systems audits and audits of operations is high. For a system assessed as having high reliability the confidence level used for sampling operations shall not be less than 60 %. For a system assessed as having low reliability the confidence level used for sampling operations shall not be less than 90 %. The maximum materiality level shall be 2 % of the expenditure referred to in paragraph 3.

Where irregularities or a risk of irregularities have been detected, the audit authority shall decide on the basis of professional judgement whether it is necessary to audit a complementary sample of additional operations or parts of operations that were not audited in the random sample in order to take account of specific risk factors identified.

The audit authority shall analyse the results of the audits of the complementary sample separately, draw conclusions based on those results and communicate them to the Commission in the annual control report. Irregularities detected in the complementary sample shall not be included in the calculation of the projected random error of the random sample.

On the basis of the results of the audits of operations for the purpose of the audit opinion and control report referred to in Article 127(5)(a) of Regulation (EU) No 1303/2013, the audit authority shall calculate a total error rate, which shall be the sum of the projected random errors and, if applicable, systemic errors and uncorrected anomalous errors, divided by the population.