The ability to contribute to a IRA (either Traditional or Roth) for a tax year, up to the filing date of that tax year (usually April 15 of the next year) has existed almost as long as IRA's have existed - decades. The whole point of doing that is so that it can be claimed on the last years tax return. That is not the quirk in the law that I was referring to.
Many people want to contribute to a Roth but their income is to high to allow it so they contribution to a non-deductible Traditional IRA instead that has no income limit. Then they immediately convert the Traditional IRA to a Roth IRA which is allowed, thus getting the money into the Roth that they could not contribute directly. That is called a "Backdoor Roth" that I thought you might be trying to do. There are many pitfalls that can cause that not to work as expected if one does not fully understand the tax law that allows it.
**Disclaimer: This post is for discussion purposes only and is NOT tax advice. The author takes no responsibility for the accuracy of any information in this post.**
