In News Release IR-2018-33 the IRS announced that it was now able to begin accepting returns claiming certain tax benefits retroactively restored for 2017 by the Bipartisan Budget Act of 2018. The three benefits that the IRS is now ready to accept returns containing are the following:

Exclusion from gross income of discharge of qualified principal residence indebtedness (often, foreclosure-related debt forgiveness),
Mortgage insurance premiums treated as qualified residence interest, and
Deduction for qualified tuition and related expenses.

These provisions had expired at the end of 2016 and Congress had not enacted legislation to extend them for an additional year until the passage of the Bipartisan Budget Act on February 9.

Note that this is not all the benefits extended by the Act, which included several energy related credits. The IRS news release notes:

The IRS is continuing to update its systems to handle returns claiming the other tax benefits extended by the new law, enacted on Feb. 9. In general, these benefits affect a smaller number of taxpayers. Taxpayers eligible for these benefits can avoid delays or possibly needing to file an amended return later, by filing after IRS systems have been updated to reflect these changes.

Taxpayers who have already filed their returns and qualify for these benefits will need to file an amended return if they wish to claim the benefits. The news release note that the processing for such an amended return can take up to 16 weeks.

A practical problem for most practitioners is that even though the IRS has updated its systems to accept returns with these items on them, tax software providers will need to update their software to be able to handle these items as well. Some vendors have already done so, and others likely will release their updates in the week or so.