To put it simple, Agile methodology is based on quick iterations. That approach implies that: We must be fast coders to complete each iteration in the scheduled time Soon or later we'll go back to that code we quickly wrote in the past If we only focus in the first statement ( be faster, my friend ), codebase quality tends to degrade, code entropy -or the codebase maintenance complexity- increases, bugs start to consume more and more time in every sprint and, in last term, software components must be fully re-coded, what can consume great part of the benefits we got by becoming agile. However if we have in mind that, in coming iterations, we'll have to refactor the code we are working on right now, we can document the technical debt we intentionally create with the purpose of fixing it in the future. In that way, when planning every iteration (or sprint) we can schedule a percentage of the coding effort to fix that debt we left, therefo