A potential change that isn’t getting too much attention is the requirement to sell securities on a FIFO basis rather than it being an option under current law. This might blindside people who hold much of their assets in mutual funds. Even if the individual uses FIFO by choice now, that doesn’t mean the fund companies have been using FIFO.
"This also would mean that mutual fund managers would also lose the ability to pick specifically which shares to sell. The change would take effect Jan. 1.
“Requiring taxpayers to treat securities as sold on a first-in, first-out basis would be disproportionately harmful to ordinary Americans who invest with funds,” said Paul Schott Stevens, president and CEO of the Investment Company Institute.
“It would increase significantly the amount of taxable distributions made to investors every year and tie the hands of fund managers as they pursue investment strategies on behalf of savers.”"
https://www.cnbc.com/2017/11/15/senate-tax-bill-boosts-taxes-on-stock-sales.html