Before 2020-21: atypical expenditure items were automatically excluded from base costs. After 2020-21: atypical expenditure were automatically included in base base costs. We therefore revisited all atypical expenditure items reported back to 2011-12 to decide whether they should be included in the base cost models. We consider that most atypical expenditure items should be included in the base cost models unless they are related to fines/penalties, truly one-off exceptional expenditure items, or do not reflect actual cost movements. This file determines and calculates atypical expenditure adjustments that need to be made to base costs. We provide a brief explanation behind our decision to exclude / include atypical expenditure items from modelled base costs in worksheets 'Water' and 'Wastewater'.