This paper critically reviews Sato’s (2023a, b) hypothesis on ellipsis constructions, specifically questioning the validity of the difference between elements elided at PF and those that meet identity criteria at LF. We support the traditional approach, aligning the elided constituent at PF with what satisfies identity in ellipsis at LF. Our study examines the contrast between inflectional and derivational elements in ellipsis, noting that inflectional elements can be included as part of the vP structure to be elided, while derivational elements cannot be. We also diverge from Kehler’s (2000) approach, focusing on the distinction between resemblance and cause/effect relations in VP/vP ellipsis. We propose that VP ellipsis typically occurs in resemblance relation and vP ellipsis does in cause/effect relation, with voice mismatches in VP ellipsis tolerated by the VP-external checking of structural Accusative Case. Discrepancies in Case feature or argument structure within vP, however, result in breach identity in ellipsis. Additionally, Case mismatches in larger constituent deletions, like TP/vP under Sluicing, are shown to significantly degrade sentence acceptability. Overall, we argue that the acceptability of mismatches in ellipsis hinges on meeting identity in ellipsis.