I had a family HDHP for the first 8 months of 2018, and while I opened an HSA account during that time. Can I continue to make contributions to my HSA between September 1st 2018 and April 15th 2019 (up to the prorated max contribution limit)? Or does the prorated limit apply to people currently on an HDHP that started mid year?
Yes, if you know your prorated HSA contribution limit, you have until April 15, 2019 to make HSA contributions for 2018 up to that limit. You don’t have to have HDHP coverage currently in order to make a contribution; you were an eligible individual for part of 2018, so you can make a 2018 contribution up to your limit.