If the bill for the eligible expenses was paid in 2016, then the 529 withdrawal that will cover those expenses also needs to happen in 2016. In your first post you said that the bill was paid in 2016 and you are asking if you can withdraw 529 funds in 2017 for those eligible expenses. If you do this, it's very likely that the 529 distribution will be considered non-qualified, meaning that the earnings portion of the distribution will be subject to tax, and potentially a 10% penalty as well.