Why the earlier deadline exists
Pass-through entities do not pay federal income tax themselves; they issue K-1s telling each owner what to report. The month’s head start exists so owners have their K-1 before the individual deadline. In practice, the K-1 arriving late is the single most common reason an individual return goes on extension.
What is due
- Form 1120-S for S-corporations, plus K-1s to shareholders
- Form 1065 for partnerships and multi-member LLCs, plus K-1s to partners
- The Oregon equivalents
- Where the PTE-E election applies, the associated entity-level obligations
The penalty is per owner, per month
Late-filing penalties for pass-through returns are assessed per shareholder or partner, per month. A four-owner partnership three months late is twelve penalty units. This is why a filed extension matters so much more here than on a personal return.
If the books are not ready
File the extension, then fix the books. A return prepared from unreconciled accounts is a guess with your signature on it, and amending later costs more than extending now. See catch-up bookkeeping.
Not sure how this applies to you?
Call 503-785-3200 or schedule an appointment. We will find a time that works.
Written by
Enrolled Agent, Oregon Licensed Tax Consultant
License number: Enrolled Agent 00160070-EA · Oregon Licensed Tax Consultant 35746-C
Heather has spent more than a decade preparing individual and business returns across the Portland metro and the Columbia Gorge, and holds unlimited rights to represent taxpayers before the IRS.
Last reviewed
This page is general information about Oregon, Washington and federal tax rules, not advice about your own return. Thresholds and rates change every year. Figures were verified as of August 2026 — check the linked official sources, or talk to us about your situation.