For some business contexts, a transaction starts with a customer making an initial purchase decision (e.g., reserving a specific car, or putting a specific product in the shopping cart), and ends when the customer pays for the chosen product if the initial decision is held on, or a new product if the initial decision is replaced. This format of transaction, which comprises two related discrete decisions, cannot be fully accommodated by existing choice models which mainly deal with either discrete or concrete decisions, or, in rare cases, a combination of one discrete decision and one continuous decision (i.e., the so-called discrete-continuous choice model which has been widely used in the telecom business to model the mobile plan subscription for each month and the minute usage in the month). More importantly, this two-step transaction adds a great deal of richness into the customers’ as well as firms’ decisions which cannot be easily uncovered with existing tools. As an example, while the first decision is made for future consumption, the second one is usually for immediate consumption. Yet, these two are related decisions and it’s likely that the second one is influenced by the first one. How customers make the two decisions and to what extent the time gap between the two affects the second decision are interesting questions that this study will explore. This proposal will complete a few on-going projects that help us better understand the customers’ and firms’ behaviours in such two-step transactions. It will also explore many new directions that are enabled by this new format of transaction.