Estimating Payments When Your Business Return Is on Extension

This is for owners of S-corps, C-corps, partnerships, and single-member LLCs.

An extension gives you more time to file, not more time to pay. Interest generally starts accruing on unpaid tax from the original due date—even if you extend. (IRS)

This guide helps you figure out whether a payment is even applicable at the entity level, and if so, how to “guesstimate” it. This is general info—not personalized tax advice—and it may not capture every special rule that applies to your situation.

Step 1 — Identify what kind of entity you have

*This changes who pays

S-Corp (Form 1120-S) and Partnerships (Form 1065)

Most S-corps and partnerships are pass-through entities, meaning the owners pay income tax on their personal returns for the company's profit, not at the corporate level. The profit (or loss) is passed through to the owners via their Schedule K1s that are prepared alongside the tax returns.

However, some S-corps and partnerships can owe entity-level tax in special situations (not common, but possible). Check your prior-year Business Tax Return for a voucher or other indication of an amount due. This is a good indication that it may owe tax this year, too.

If the business itself owes tax, it’s still due by the original deadline—an extension does not extend time to pay.

C-Corp (Form 1120)

C-corps are typically tax-paying entities. If the corporation owes income tax for the year, that tax is due by the original return due date—even if you extend the filing.

Single-Member LLC (disregarded entity; usually Schedule C/E/F on the owner’s 1040)

A single-member LLC (that has not elected corporate taxation) usually does not file a separate federal business income tax return. The “extension + payment” lives on the owner’s personal extension/payment process. Refer to our article on estimating individual income tax payments required.

Step 2 — Know your deadline (by entity type)

Deadlines are based on your tax year-end:

• S-corp / Partnership: due the 15th day of the 3rd month after year-end (March 15th for calendar-year operators)

• C-corp: due the 15th day of the 4th month after year-end (April 15th for calendar-year operators)

• Individuals: due the 15th day of the 4th month after year-end. (April 15th for calendar-year operators). Refer to our article on estimating individual income tax payments required.

Form 7004 must be filed by the return’s due date to extend the filing deadline.

Step 3 — Decide if an entity-level payment applies

C-corp

You generally do need to consider an extension payment if you expect tax due.

Quick way to estimate a reasonable payment:

1. Pull last year’s corporate return and find:

   • Prior-year total tax

   • Prior-year total payments/credits

   • Prior-year balance due/refund

   
   

2. Ask: is this year likely similar (profit, major transactions, credits) or very different?

   
   

3. Pick one approach:

   • Same-as-last-year: pay roughly what you owed last year (adjust upward if profit increased).

   • Rough current-year estimate: use year-end financials to estimate taxable income × estimated effective tax rate, then subtract payments already made.

Paying something is generally better than paying nothing, because interest accrues from the original due date on any unpaid tax.

S-corp or Partnership

Since the tax liability lies with the individual owners, they must individually determine whether a payment should be made. If the extension of their business K1 requires them to file an extension on their personal tax return, the owners may need to make a payment alongside their extensions.

Refer to our article on estimating individual income tax payments required.

Step 4 — Where to pay (if a payment applies)

• For federal payments, use irs.gov/payments or your entity's login at https://www.irs.gov/businesses/business-tax-account

• For state payments, use the state’s department of revenue site

  
  

Step 5 — Save proof

Save the confirmation (PDF/screenshot). You’ll want it when reconciling payments while finalizing the return.

Final Notes

• Extension = more time to file, not pay. 

• Interest generally runs from the original due date on unpaid tax (even with an extension).

• State rules can create entity-level payments even when the federal doesn’t (common in some states for LLC fees/franchise taxes).