I had a qualifying event which resulted in a new High Deductible Health Plan (HDHP) with new HSA active as of 2021-01-01. I've been making contributions pre-tax through my employer every paycheck. Can I contribute for the 2020 tax year, even though the account has only existed in 2021, if it's before the tax-filing deadline? This site seems to say yes:
You can make a contribution to a new HSA for a given tax year if you open the account prior to April 15, the following calendar year. However, HSA funds may not be used to cover qualified medical expenses incurred prior to the account opening.
But, I'd like confirmation from an official source and I haven't been able to find something from the IRS that says so one way or another -- I realize I can't claim expenses from before the account was open, I'm only concerned about making contributions.
Clarification: High Deductible Health Plan (HDHP) coverage and HSA account were active as of 2021-01-01. I had neither before 2021.