Countries shall take all appropriate measures to reduce item and unit non-response. Prior to imputation countries shall make all reasonable efforts to use other data sources.

Core variables, for which no missing value shall be accepted, nor imputation permitted are:

• A1, A2tot, B1a, B1b, B2a(QL), B2b(QL) B2c(QL), B2d(QL) B2e(QL), F1tot.

Key variables, for which every effort should be made to avoid missing values and for which imputation is recommended are:

• A3, A4, A5, C1tot, C3tot, C7sub, C7tot, PAC.

Imputation for item non-response shall be recommended within the following general limits:

1. 1.

   When a record contains less than 50 % of variables presented then this record shall normally be considered as a unit non-response.

2. 2.

   For a single NACE Rev.2/size cell imputations shall not be allowed if more than 50 % of the responding enterprises have missing data for more than 25 % of the quantitative variables.

3. 3.

   For a single NACE Rev.2/size cell, no imputation shall be performed on a quantitative variable if the proportion of responding enterprises for that particular variable is less than 50 %.

4. 4.

   For a single NACE Rev.2/size cell, no imputation shall be performed on a qualitative variable if the proportion of responding enterprises for that particular variable is less than 80 %.

Quantitative and qualitative variables are identified in Annex I.

Member States shall calculate and transmit a weight to be applied to each data record together with any auxiliary variables, which may have been used in the calculation of this weight. These auxiliary variables should be recorded as the variables RESPEXTRA1, RESPEXTRA2, RESPEXTRA3 as necessary. The methodology adopted for establishing the weights shall be detailed in the quality report.