First off let me state that “may” in the title means that there are always those rare cases and exceptions to almost everything when it comes to accounting. Since we’re not about those rare situations, but more wanting to state the basics, we’re going to skip this. It’s just to let you know that there are exceptions as always. 

Now, if you’ve decided to change accounting presentation and / or classification in your reports, it means your future figures are about to change. It is either how you’re going to group them from now on, on which statements your presenting them etc. It’s the format that’s changing.

Why would you change your previous year figures? Well, simply because of something we call “consistency”. You do want your figures still to be comparable and as such, when you’re changing accounting presentation and / or classification, you’ve got to go back in time and make those changes into the past as well. What it in practice means is that you change last year’s figures and for all the other years the effect if any is carried into “retained earnings”. If it’s just a presentational change, it’s unlikely there’s any such effect, but just to give you a hint.

Whenever you’ve made your careful considerations and decided to change accounting presentations, always consider and apply those changes retrospective.