Healthcare.gov on the backend had to interface with systems from a bunch of different government agencies and companies. Many of those systems had not been desi

Healthcare.gov on the backend had to interface with systems from a bunch of different government agencies and companies. Many of those systems had not been designed to interface to other agency and company systems. They all had their own APIs and data formats. That all greatly increased the complexity of the project. An IRS e-filing system would just be adding a public interface for taxpayers to a system they already have.