When to file Form 3115 and what happens if you miss the deadline

Most founders who ask about Form 3115 want to know two things: when is it due, and what happens if it is late.

The answer to the first question is more layered than people expect, because Form 3115 does not have a single universal due date. The deadline depends on whether the change being requested is an automatic change or a non-automatic one, which entity type is filing, and whether an extension has been filed for the underlying federal tax return. For most startups, the Form 3115 deadline is the same as the deadline for their annual tax return, including any extensions, which means the decision window is both wider and more contingent on other filings than founders typically realise.

The answer to the second question is simpler, and more serious. Filing Form 3115 late generally means losing the ability to make the accounting method change for that year. The IRS grants late filing relief only in unusual and compelling circumstances, and that standard is not easy to meet.

This guide explains the filing timeline for both automatic and non-automatic changes, the Form 1120 and October 15 connection that matters for C-Corps, and what options exist when a deadline has been missed.

Why the due date is tied to the tax return

Form 3115 is not filed on its own as a standalone document, at least not for the type of change most startups need. For an automatic accounting method change, the taxpayer files the original Form 3115 by attaching it to their timely filed federal income tax return for the year in which the change takes effect. The due date of Form 3115 is therefore the due date of the underlying return, including any extensions.

This means there is no separate Form 3115 deadline to track on its own. What matters is the return deadline. If the return is filed on time, the attached Form 3115 is on time. If the return is filed late, the Form 3115 is also treated as late, and the method change may not be valid for that year.

The practical consequence of this structure is that any decision about extending a return deadline automatically extends the window for filing a Form 3115 automatic change request alongside it. For founders who are still working through the decision to switch from cash to accrual, or who discovered a depreciation error late in the year, filing a return extension can preserve the option to include Form 3115 in the extended filing without any additional steps specific to the form.

Deadlines for automatic changes by entity type

For automatic accounting method changes, which cover the most common situations startups encounter, the filing deadlines follow the underlying return.

C-Corporations filing Form 1120 have an original due date of April 15 for calendar-year filers. Filing Form 7004 by April 15 extends the return deadline to October 15. Form 3115 for an automatic change must be attached to the timely filed return, which for an extended calendar-year C-Corp means the original or extended Form 1120 filed by October 15. This is the most common scenario for startups.

S-Corporations filing Form 1120-S have an original due date of March 15 for calendar-year filers, with a six-month extension to September 15 available via Form 7004.

Partnerships and multi-member LLCs filing Form 1065 have an original due date of March 15 for calendar-year filers, with a six-month extension to September 15 available via Form 7004.

Sole proprietors and single-member LLCs file on Schedule C with the individual Form 1040, due April 15, with a six-month extension to October 15 available via Form 4868.

In every case, the extended deadline applies only if the extension form was properly filed and accepted before the original due date. A late-filed extension does not preserve the original deadline.

The October 15 connection for C-Corps

For calendar-year C-Corporations, October 15 is not just the extended Form 1120 deadline. It is simultaneously the last date to attach a Form 3115 automatic change request for the tax year that just ended.

This matters because Form 3115 and Form 1120 are processed together. The original Form 3115 is physically attached to the return when it is filed. If a C-Corp files Form 7004 by April 15 and then files its Form 1120 on October 15, it has until October 15 to include the Form 3115 with the return. That six-month extension window is available for both filings simultaneously.

The implication is direct for founders who are deciding whether to switch accounting methods or make a depreciation correction for the prior tax year. October 15 is the last available date to make an automatic method change for the calendar year that just ended. A C-Corp that decides in late September that it needs to switch from cash to accrual for the prior year can still do so, provided the Form 1120 has not yet been filed and the extension was properly obtained in April. Once October 15 passes and the return is filed, or once October 15 passes without a filed return and the return becomes late, the window for that tax year closes.

It also matters in the other direction. A C-Corp that fails to file Form 7004 by April 15 loses the extension window for both the return and the Form 3115. Filing Form 3115 after April 15 without a valid extension means both documents are late. The IRS instructions confirm that a timely filed Form 3115 attached to a timely filed return is what grants automatic consent to the method change. A return and Form 3115 filed one day after the deadline without a valid extension are treated as late.

There is one narrow IRS-provided safety valve worth knowing, though it is more limited than it sounds. Rev. Proc. 2015-13 provides an automatic six-month extension, measured from the federal return's original due date excluding any granted extension, for certain automatic-change requests. However, this provision has specific conditions that must all be met. The taxpayer must have timely filed the original federal return, including any valid extension. The taxpayer then files an amended return within the six-month period implementing the method change, attaches the original Form 3115 to that amended return, files the signed Ogden duplicate copy no later than the amended return filing date, and includes a statement confirming the filing is being made under section 301.9100-2(b).

This is not a general permission to wait until October 15 after missing April 15, and it is not available to a taxpayer who missed both the original deadline and the extension deadline. It is a specific relief mechanism for a taxpayer who filed the original return on time but then identified a method change opportunity within the subsequent six months. A tax professional should analyze the specific facts before relying on this provision.

The duplicate copy requirement for automatic changes

Filing Form 3115 for an automatic change involves two separate documents going to two separate addresses. Failing to send both is one of the most common procedural errors founders and their accountants make.

The original Form 3115 is attached (unsigned) to the federal tax return and filed with the return through the usual filing channel, whether that is electronically through the IRS e-file system or by paper mail to the appropriate service center.

A signed duplicate copy of the same Form 3115 must be sent separately to the IRS office in Ogden, Utah. The current IRS instructions provide two address options for the duplicate copy: by mail to Internal Revenue Service, Ogden, UT 84201, M/S 6111, or by private delivery service to Internal Revenue Service, 1973 N. Rulon White Blvd., Ogden, UT 84201, Attn: M/S 6111. The duplicate may also be sent by fax to 844-249-8134.

The timing requirement for the duplicate copy is specific. It must be sent no earlier than the first day of the year of change and no later than the date the original is filed with the federal return. In practice, most practitioners send the duplicate copy at the same time the return is filed. The IRS does not send acknowledgments of receipt for automatic change requests, which means there is no confirmation that the duplicate copy arrived. Sending it by a traceable method, whether certified mail with return receipt or a private delivery service with tracking, creates a record.

If the duplicate copy is not sent, the automatic consent for the method change may not be valid. The IRS's position under Rev. Proc. 2015-13 is that timely filing and compliance with the automatic change procedures, which include the duplicate copy requirement, are what grant consent. A Form 3115 attached to the return without the corresponding duplicate copy does not fully comply with those procedures.

Deadlines for non-automatic changes

Non-automatic accounting method changes operate on a completely different timeline. Instead of attaching the form to the filed return, the taxpayer files Form 3115 with the IRS National Office in Washington, D.C., during the tax year for which the change is requested, before the return is filed. The IRS instructions specifically note that Form 3115 for a non-automatic change should be filed as early as possible during the year of change to give the IRS adequate time to review and respond before the return due date.

The reason for this is that a non-automatic change requires advance consent from the IRS. The IRS reviews the application and issues a letter ruling approving or denying the change. The IRS normally sends an acknowledgment of receipt within 60 days. Founders who wait until late in the year to file a non-automatic change request may find that the IRS has not processed the application by the time the return needs to be filed, creating a complication for the return itself.

Non-automatic changes also require a user fee. The amount is set annually in Rev. Proc. 2023-1 and its successors. There is no user fee for automatic changes. This is one of several reasons that qualifying for the automatic change procedures, when possible, is significantly more practical for most startups.

What happens when Form 3115 is filed late

The IRS instructions are direct on this point: a filer that fails to timely file Form 3115 will generally not be granted an extension of time to file except in unusual and compelling circumstances. The standard for relief under Regulations section 301.9100-3 requires that the taxpayer acted reasonably and in good faith and that granting relief would not prejudice the government's interests. This standard is real and is not satisfied simply by showing that the deadline was missed by a small amount or that the oversight was unintentional.

The consequence of a late Form 3115 is that the accounting method change is not valid for the requested year. The taxpayer must either wait until the following tax year to file a valid request, continue using the existing method for the current year, or pursue relief under the applicable regulations if the circumstances support it.

A real-world example drawn from IRS published guidance illustrates how little flexibility exists. In IRS Written Determination 202503014, a consolidated C-Corp taxpayer filed Form 3115 as part of a return that was submitted one day after the extended due date due to technological issues with the tax preparation software. The return was accepted the following day, and the taxpayer sought to have the Form 3115 treated as timely. The IRS ultimately granted relief under the specific facts of that case, but the analysis makes clear that a one-day delay without a clear and documented reason would not normally receive the same treatment. The relief was based on the technological failure being outside the taxpayer's reasonable control and the taxpayer having otherwise fully complied with all requirements.

This is not a precedent for treating late Form 3115 filings as manageable risks. It illustrates that relief exists in the right facts, not that lateness is routinely forgiven.

The five-year rule and how it affects timing decisions

One timing constraint that founders often learn about too late is the five-year rule for automatic changes. Under Rev. Proc. 2015-13, an applicant generally cannot make an automatic accounting method change for the same item if it made or requested a change for that same item during any of the five tax years ending with the requested year of change. This restriction applies to both overall method changes and specific item changes.

For most early-stage startups, this rule is not immediately relevant because they have not previously filed a Form 3115. But it becomes relevant in two situations. First, a startup that switches from cash to accrual early and later wants to make a further adjustment to a specific item may find that the five-year clock is running from the first change. Second, a startup that is acquired or merges with another entity may inherit the acquirer's change history, which can affect eligibility.

There are exceptions within the List of Automatic Changes that waive the five-year restriction for specific DCNs, and some changes can be made outside the automatic procedures even within the five-year window by filing under the non-automatic procedures. The five-year rule is not an absolute prohibition, but it is a constraint that needs to be checked before assuming a change is available in a given year.

Timing the decision relative to a fundraise

For founders specifically, the Form 3115 filing deadline often becomes relevant in the context of a Series A fundraise or a due diligence process. Institutional investors typically expect accrual-based financial statements. If a startup has been on cash basis and needs to switch before or alongside a raise, the timing of the switch relative to the tax year matters.

The most important point is that the switch must happen in a tax year for which the Form 3115 can still be timely filed. A startup that wants to show accrual-based financials for the prior year but has already passed the deadline for that year's return cannot retroactively change the accounting method. The change takes effect in the year of change, and the Section 481(a) adjustment accounts for the cumulative difference from prior years going forward. Understanding this helps founders work backward from the fundraise timeline to determine when the method change needs to be formally initiated.

A startup heading into a fundraise in Q3 of a given year that wants accrual-basis financials for the current tax year should initiate the Form 3115 preparation early enough to include it with the current year's return, whether that is filed at the original deadline or by extension. Waiting until the return has already been filed and then wanting to add a method change is not possible after the fact.

How Inkle handles Form 3115 timing

Inkle's tax team manages accounting method changes as part of the annual compliance process for US startups. When the right moment for a cash-to-accrual switch arrives, whether triggered by investor requirements, a gross receipts threshold, or a depreciation correction that has been sitting unaddressed, Inkle handles the preparation of Form 3115, the calculation of the Section 481(a) adjustment, and the coordination of both the original filing with the return and the duplicate submission to Ogden.

For founders approaching a Series A or working through a first audit, getting the method change documentation right the first time matters more than most founders expect until it becomes a diligence issue.

Learn more about Inkle's tax filing services.

Frequently asked questions

When is Form 3115 due for a calendar-year C-Corp? 

For a calendar-year C-Corp making an automatic accounting method change, Form 3115 must be attached to the timely filed Form 1120, including extensions. If Form 7004 was filed by April 15, the extended deadline for both Form 1120 and the attached Form 3115 is October 15. If no extension was filed, the original deadline is April 15.

Can I file Form 3115 separately from my tax return? 

For automatic changes, no. The original Form 3115 must be attached to the timely filed federal tax return for the year of change. However, a signed duplicate copy must also be sent separately to the IRS office in Ogden, Utah, no earlier than the first day of the year of change and no later than the date the original is filed with the return.

What happens if Form 3115 is filed late? 

A late Form 3115 generally means the accounting method change is not valid for the requested year. The IRS grants late filing relief only in unusual and compelling circumstances under Regulations section 301.9100-3. To meet that standard, the taxpayer must show it acted reasonably and in good faith and that granting relief will not prejudice the government's interests. Factors that may support reasonable cause include requesting relief before the IRS discovers the failure, an intervening event genuinely beyond the taxpayer's control, or reasonable reliance on written IRS advice or a qualified tax professional. Factors that weigh against relief include using hindsight, having been informed of the requirement but choosing not to act, or attempting to alter a position connected with an accuracy-related penalty. An automatic six-month extension from the original return due date may be available in limited circumstances under Regulations section 301.9100-2, but that provision requires the original return to have been timely filed and imposes additional conditions described elsewhere in this post.

Is there a user fee for filing Form 3115? 

There is no user fee for automatic change requests. A user fee is required for non-automatic change requests. The fee schedule is set annually in Rev. Proc. 2023-1 and its successors.

Can I still make a method change for last year if I have already filed my return? 

No. Once a return is filed, the window for attaching Form 3115 for an automatic change closes for that tax year. The method change would need to be made in a subsequent year's return. If the return has not yet been filed and the deadline has not passed, the Form 3115 can still be included.

What is the five-year rule for Form 3115? 

Under Rev. Proc. 2015-13, a taxpayer generally cannot make an automatic accounting method change for the same item if it made or requested a change for that same item during any of the five tax years ending with the requested year of change. Some exceptions exist within the List of Automatic Changes for specific designated change numbers.