The TB_PREV indicator reports the proportion of ART patients who started on a standard course of TB Preventive Treatment (TPT) in the previous reporting period who completed therapy. For example, if reporting is for Q1 and Q2 of a fiscal year (e.g., October 2019 to March 2020), then the denominator would include those that were started on TPT in Q3 and Q4 of the previous fiscal year (e.g., April to September 2019). If a TPT register is being used, then this would require simply framing out the dates that define the previous reporting period and counting all those who started TPT.