Why it matters
Each state sets its own rules, so check the state's current instructions before you promise a client a composite. Wisconsin does not require composites, but Alabama does and Oregon must file one when an owner asks. In Wisconsin an owner who wants credits or itemized deductions has to leave the composite and file Form 1NPR. Ask the client, "Do you want to be included, and do you have other income from this state?"
Example
A calendar-year partnership has four Illinois-resident partners with Wisconsin-source income. Three agree to a Wisconsin composite on Form 1CNP, due April 15 and generally filed electronically. The fourth claims itemized deductions, so she is left out and files Form 1NPR herself. Pass-through withholding on Form PW-1 is due March 15 and has to be filed before the composite.
Related terms
Questions about Composite return
Does the IRS have a composite return?
Composite returns are a state mechanism. The sources checked for this page, Wisconsin, Oregon and Alabama revenue rules, treat them as state returns filed by the entity for its nonresident owners. Each owner still reports the same income from Schedule K-1 (Form 1065) on a federal return.
Does a composite return extend the payment date too?
No. Alabama states that an extension of time for filing is not an extension of time for payment of tax, and its calendar year 2025 return was due on or before March 15, 2026. Oregon allows a six month extension to file. Confirm the 2026 dates in each state's instructions when they are published.
Who cannot join a composite return?
It depends on the state. Oregon excludes Oregon residents and partnerships, and requires each owner to make a separate election each tax year. Wisconsin excludes estates and trusts filing for their beneficiaries and owners who want credits or itemized deductions.