International Financial Reporting Standards (IFRS) are often described as principles-based; however, we show that IFRS and Australian pre-IFRS expense-related standards are more rules-based than pre-IFRS expense disclosure in New Zealand. Thus, we examine expense disclosure in New Zealand and Australia around IFRS adoption to provide evidence on the effect of more or less rules-based standards on voluntary disclosure. First, we add to the rules versus principles-based standards debate by finding higher voluntary expense disclosure under more rules-based standards (e.g. IFRS). This contrasts with expectations, as we would expect fewer voluntary disclosures under more rules-based standards as there would be fewer possible voluntary disclosures. Second, we document that New Zealand firms have significantly less voluntary expense disclosure than size- and industry-matched Australian firms in both the pre- and post-IFRS period. However, all measures of expense disclosure significantly improved post-IFRS for New Zealand, whilst little change occurred for Australian firms. Thus, there is greater financial statement comparability across these countries post-IFRS, but not full harmonization. Third, we show that the relationship between most firm characteristics and expense disclosure is weaker post-IFRS. In addition, cross-listed firms and loss-making firms have a higher level of expense disclosure, as contrasted with firms in the investment and property industry which have a lower percentage of unspecified expenses but also report fewer voluntary expenses.