There is no fixed time for admissions decisions to be made, and it is common for offers to be sent out as late as April. Several reasons explain possible delays in offers being sent out:

• In some cases it is because your application is not yet complete, typically because one or more letters of recommendation have not arrived. If you are applying for admission with aid, we usually will notify you in March if your application is incomplete.
• Another source of delay can occur because the Admissions Committee is waiting to hear from one or more IU professors, to see if they think that you could be a potential advisee for them. This is part of the process of trying to make sure that Ph.D. students in particular have at least one professor who could direct the student's dissertation.
• In the event that you are nominated for a university fellowship, the application has to wend its way through several university committees. Offers are delayed so that the fellowship (if approved) can be offered along with admission.
• Sometimes the department is waiting to determine how many offers can be made for teaching assistantships, or individual professors are waiting to find if one of their grant proposals has been funded by the NSF or other agencies.
• International applications have to be processed by the International Admissions Office before we can send out an offer. In particular the IA has to officially approve the undergraduate degree as being "bachelor's equivalent", and that introduces delays. In the past few years, however, the CS department has been given fast-track processing.
• Finally, sometimes the first round of offers has gone out and we are waiting to see if any students decline those offers. In this case, a second round of offers goes out but these are late in the season.