The IRS will continue to process tax returns that contain remittances and all e-filed returns, but will not process paper returns that do not contain remittances. The IRS has not announced the postponement of any return filing deadlines, such as the October 15 deadline for individual tax returns on extension.

During the shutdown, all IRS audits and examinations will stop. All nonautomated collection activity will also stop. However, IRS criminal law enforcement and undercover operations will continue.

The shutdown brings a stop to all IRS taxpayer services, such as responding to taxpayer inquiries, as well as the practitioner priority service.

During the shutdown, the IRS will take steps to protect ongoing bankruptcy, lien, and seizure cases and to prevent lapses in the statute of limitation.

The IRS website (irs.gov) will stay up, with a skeleton staff of six to maintain it. This staff will focus on ensuring the site stays up, that emergency messages are posted, and changes can be made. It is not clear if any new content will be posted to the site.

Federal courts will remain open for approximately 10 business days. All scheduled proceedings and deadlines remain in effect, and the electronic case management system will stay in operation. Around Oct. 15, the federal judiciary will reassess its situation and determine whether courts can stay open. If the federal courts do shut down, the IRS Chief Counsel personnel would be placed on nonduty status.

Forty-five employees of the National Taxpayer Advocate Service will remain on the job. They have been identified as necessary for ensuring that statutory deadlines are met.

The government will continue to mail out Social Security checks, since they are funded out of an indefinite appropriation. IRS employees who support this function will continue to work during the shutdown.

The U.S. Postal Service will continue to function during the shutdown because it acts as an independent agency and is not funded by the federal government.

All IRS headquarters and administrative functions will shut down (although the commissioner will not be furloughed).

Approximately 86,000 IRS employees will be furloughed, that is, placed "in a temporary status without duties and pay because of lack of work or funds or other nondisciplinary reasons".
 
The IRS's contingency plan covers the first five business days of the shutdown (i.e., through next Monday). After that, if the shutdown continues, the IRS deputy commissioner for operations support will assess what needs to be done.