US Tax Deadlines, Extensions and Penalties: The Full Calendar

Most American tax pain is caused by dates rather than rates. The individual return is due on 15 April following the tax year, moving to the next business day when that falls on a weekend or holiday. Around that anchor sit a handful of other deadlines that catch people out every year, and a penalty regime that treats filing late and paying late very differently.

Quarterly estimated tax payments are due on 15 April, 15 June, 15 September and 15 January. They apply to anyone whose income is not fully covered by withholding: freelancers, landlords, investors with significant dividends or gains, retirees taking distributions without withholding, and employees whose W-4 is set too low. The instalments are not equal quarters of the calendar, a quirk that trips up first-time filers who assume the second payment is due in July.

Information returns arrive earlier. Employers must furnish W-2s and most payers must furnish 1099s by 31 January, so if a form has not appeared by mid-February it is worth chasing rather than guessing. Partnerships and S corporations file their own returns by 15 March, which matters to individual partners and shareholders because their Schedule K-1 is needed before the personal return can be completed. C corporations generally file by 15 April.

An extension is widely misunderstood. Filing Form 4868 gives an automatic six months to submit the return, moving the deadline to 15 October. It does not give you extra time to pay. Tax owed on 15 April remains owed on 15 April, and interest plus a late-payment penalty accrues from that date regardless of the extension. The correct use of an extension is when information is genuinely missing — a late K-1, an unresolved foreign tax figure — and it should be accompanied by a payment of your best estimate.

The penalty structure rewards filing even when you cannot pay. Failure to file costs 5 per cent of the unpaid tax per month up to 25 per cent. Failure to pay costs 0.5 per cent per month, also capped at 25 per cent. The difference is tenfold, so lodging on time with a partial payment is dramatically cheaper than staying silent. Interest runs on top of both at a rate reset quarterly.

If you cannot pay in full, the IRS has formal routes that are better than avoidance. A short-term payment plan gives up to 180 days. A long-term instalment agreement spreads the debt over up to 72 months and can often be set up online without speaking to anyone. An offer in compromise settles for less than the full amount but requires genuine inability to pay and full disclosure. First-time penalty abatement is available to taxpayers with a clean prior three-year record and is granted more often than most people expect — you simply have to ask.

Americans abroad get an automatic two-month extension to 15 June, with a further extension available to 15 October. Separate foreign reporting deadlines apply: the FBAR for foreign financial accounts above the aggregate threshold, and Form 8938 for specified foreign financial assets. Penalties in this area are severe and are assessed per form, not per dollar of tax, which is why non-resident filers should diarise these dates independently of the main return.

The simplest protection is a calendar with five recurring entries: the four estimated payment dates and 15 April. Add 31 January as a check that all your information returns have arrived, and 15 October if you habitually extend. Filing on time, even imperfectly, is the single cheapest tax decision available to any US taxpayer.