Updated October 16, 2026. Quick answer: Boxes 18 and 19 of Schedule K-1 (Form 1120-S) are check boxes for a shareholder whose S corporation has more than one activity. The 2025 instructions say “When the corporation has more than one activity for at-risk purposes, it will check this box and attach a statement.” “When the corporation has more than one activity for passive activity purposes, it will check this box and attach a statement.”
What boxes 18 and 19 report
On the form, the two lines read “More than one activity for at-risk purposes” and “More than one activity for passive activity purposes”, each followed by an asterisk that points to the attached statement. This page covers the shareholder’s side of a K-1 you received. Every other box is set out on the Schedule K-1 (Form 1120-S) boxes overview.
Box 18: more than one activity for at-risk purposes
“When the corporation has more than one activity for at-risk purposes, it will check this box and attach a statement.” “Use the information in the attached statement to correctly determine your at-risk limitations.” “For more information, see At-Risk Limitations, earlier.”
The reason the activities are separated is stated in the at-risk section: “Since at-risk limitations apply for each activity, you should get a separate statement of income, expenses, and other items for each activity from the corporation.” “Note: Box 18 of Schedule K-1 will be checked when a statement is attached.”
Box 19: more than one activity for passive activity purposes
“When the corporation has more than one activity for passive activity purposes, it will check this box and attach a statement.” “Use the information in the attached statement to correctly determine your passive activity limitations.” “For more information, see Passive Activity Limitations, earlier.”
The passive section describes what the statement contains: “If the corporation has more than one activity, it will attach a statement to your Schedule K-1 that identifies each activity (trade or business activity, rental real estate activity, rental activity other than rental real estate, portfolio income, etc.) and specifies the income (loss), deductions, and credits from each activity.” “Note: Box 19 of Schedule K-1 will be checked when a statement is attached.”
The at-risk limitation these boxes refer to
“Generally, if you have (a) a loss or other deduction from any activity carried on as a trade or business or for the production of income by the corporation, and (b) amounts in the activity for which you aren’t at risk, you will have to complete Form 6198, At-Risk Limitations, to figure your allowable loss for the activity.”
“The at-risk rules generally limit the amount of loss and other deductions that you can claim to the amount you could actually lose in the activity.” “These losses and deductions include a loss on the disposition of assets and the section 179 expense deduction.”
The instructions list amounts that are not at risk. One example: “protected against loss by a guarantee, stop-loss agreement, or other similar arrangement”. A loss that is blocked is not gone: “Any loss from a section 465 activity not allowed for this tax year will be treated as a deduction allocable to the activity in the next tax year.” Form 6198 is covered on the Form 6198 page.
The passive activity limitation these boxes refer to
“Section 469 provides rules that limit the deduction of certain losses and credits.” “These rules apply to shareholders who:” “Are individuals, estates, or trusts; and” “Have a passive activity loss or credit for the tax year.”
The instructions then define the term. “Generally, passive activities include: 1. Trade or business activities in which you didn’t materially participate, and” “Passive activities don’t include the following. 1. Trade or business activities in which you materially participated.”
Passive losses are figured on their own form. “If you have a passive activity loss or credit, use Form 8582, Passive Activity Loss Limitations, to figure your allowable passive losses”. The form is covered on the Form 8582 page.
Rental real estate is treated activity by activity: “Each interest in rental real estate is a separate activity, unless you elect to treat all interests in rental real estate as one activity.” Rental income is reported on the Schedule E page.
Material participation depends on the activity
Because the statement splits the corporation into activities, the participation tests apply to each one. “You must determine if you materially participated (a) in each trade or business activity held through the corporation”. “All determinations of material participation are based on your participation during the corporation’s tax year.”
For individuals, the first tests read: “You participated in the activity for more than 500 hours during the tax year.” “Your participation in the activity for the tax year constituted substantially all the participation in the activity of all individuals”. “You participated in the activity for more than 100 hours during the tax year, and your participation in the activity for the tax year wasn’t less than the participation in the activity of any other individual (including individuals who weren’t owners of interests in the activity) for the tax year.”
Where these limits sit in the order
The instructions list four limits and put them in a fixed order: “These limitations and the order in which you must apply them are as follows: the basis limitations, the at-risk limitations, the passive activity limitations, and the excess business loss limitations.” The amounts printed in Part III are before any of them. “The amounts shown in boxes 1 through 17 reflect your share of income, loss, deductions, credits, and other items from corporate business or rental activities without reference to limitations on losses, credits, or other items”.
“When applicable, the passive activity limitations on losses are applied after the limitations on losses for a shareholder’s basis in stock and debt and the shareholder’s at-risk amount.”
Basis is the shareholder’s own job to track. “Any losses and deductions not allowed this year because of the basis limit can be carried forward indefinitely and deducted in a later year subject to the basis limit for that year.” “You are responsible for keeping the information needed to figure the basis of your stock in the corporation.”
The fourth limit is separate from the two the boxes cover: “Losses attributable to your trade or business may be limited, pursuant to section 461(l).”
Other K-1 pages on this site
The partnership version of this form is read on the Schedule K-1 (Form 1065) boxes page. Estates and trusts receive a third version, covered on the estates Schedule K-1 page.
Which revision applies
The edition read for this page is the 2025 Shareholder’s Instructions for Schedule K-1 (Form 1120-S) and the 2025 Schedule K-1 (Form 1120-S) itself, which are the revisions irs.gov served when they were read on 2026-10-16. Check the revision printed on the Schedule K-1 you received and the matching instructions, because a later edition can change the box layout, the code letters and the reporting lines.
Common mistakes
- Treating one at-risk result as covering the whole corporation. The instructions say at-risk limitations apply for each activity, so a checked box 18 means the attached statement must be used activity by activity.
- Ignoring box 19 when passive losses are involved. The instructions say to use the attached statement to correctly determine the passive activity limitations, and the statement specifies income, deductions and credits from each activity.
- Applying the passive rules before basis and at-risk. The instructions say the passive activity limitations on losses are applied after the limitations for stock and debt basis and the shareholder’s at-risk amount.
Related: Form 6198 at-risk limits, Form 8582 passive activity losses, Schedule E (Form 1040), Schedule K-1 (Form 1065) boxes explained, and Schedule K-1 for estates.
Sources
- 2025 Shareholder’s Instructions for Schedule K-1 (Form 1120-S): https://www.irs.gov/pub/irs-pdf/i1120ssk.pdf
- Schedule K-1 (Form 1120-S) (2025), Shareholder’s Share of Income, Deductions, Credits, etc.: https://www.irs.gov/pub/irs-pdf/f1120ssk.pdf
Read from the IRS documents linked above on October 16, 2026. General information, not tax advice. Your own facts decide the outcome, and a preparer, the account provider or the IRS is the right place to confirm anything consequential.