The website -- whose Oct. 1 launch was a debacle -- was hindered in part by substandard efforts from the lead contractor, CGI Federal, the newspaper said.
Officials at the Centers of Medicare and Medicaid Services, the federal agency tasked with overseeing the website's creation, began peppering CGI with questions as early as August after government officials learned the company had fewer people working on the project than promised.
It had also become increasingly clear much of the site's promised functionality was in jeopardy as outside testing began on elements of the site, the Post said.
The problems came to a head Aug. 22, when a meeting between CGI and CMS laid bare the full extent of failures, the report said.
The company had listed dozens of website features promised to be up and running Oct. 1, the site go-live date. Each feature was given a rating by CGI -- high, medium or low -- as to its confidence it would be ready.
Documents the Post said it examined showed many items failed or weren't complete by Oct. 1, including 45 features CGI had said it was highly confident would work.
A CGI spokesman said the company would not comment on the HeathCare.gov project because of confidentiality agreements with the government.