Costs can only be incurred during the active period of research, i.e. after the start date and before the end date of the grant. After the end date, purchases can be charged if the goods were physically received before the end date. The start date is determined by the contract. Where a starting certificate is required e.g. for Research Councils or Wellcome Trust, then the start date is usually determined by the day the first person begins work on the project - see Starting certificates.