The Tax Nobody Withholds
The first year of self-employment ends badly for a great many people, and almost always for the same entirely preventable reason.
Thresholds, rates and due dates change, and whether you owe estimated payments depends on your full tax position. Confirm with a CPA or at irs.gov. This is not tax advice.
For every year you were employed, an invisible system ran in the background. Money left each paycheck before you saw it, and in April the sums were roughly settled.
That system has stopped. Nothing replaced it, and nobody tells you.
What the system is now
If you expect to owe more than a modest threshold when you file, you are generally expected to pay tax during the year in four instalments, rather than all at once afterwards.
The due dates are not quarterly in the ordinary sense — they fall roughly in April, June, September and January, with the last covering the previous year. Confirm the exact dates each year, because they shift for weekends and holidays.
Two taxes are being covered: ordinary income tax, and self-employment tax — currently 15.3% on net self-employment earnings, being both halves of Social Security and Medicare. The second one is what catches people, because it exists on top of income tax and had never been visible before.
What goes wrong
The pattern is reliable.
Year one goes well. Money comes in, feels like income, gets spent as income. No estimated payments are made, because nobody mentioned them.
The following April produces a bill for the whole year's tax, plus self-employment tax, plus a penalty for not having paid along the way — and it arrives at the same moment as the first payment for the new year.
That is how first years end, and it is entirely avoidable.
The safe harbour, which is the useful bit
There is a provision worth knowing by name, because it converts an unpredictable problem into an arithmetic one.
Broadly: if you pay in at least 100% of last year's total tax — 110% if your income was above a threshold — you are generally protected from underpayment penalties, even if you end up owing more. Paying at least 90% of the current year's tax generally works too.
Why that matters: last year's number is already known. You do not have to forecast a volatile first year accurately. You can pay a known figure in four instalments, and settle the difference at filing without penalty.
Ask a CPA this exactly: what is my safe-harbour number, and what should each of the four payments be? It is a short question with a specific answer, and it removes most of the anxiety from the first two years.
Making it survivable
Separate the money as it arrives, not at quarter end. A fixed percentage of every payment received, moved immediately somewhere you do not look. This is what the separate account is for.
Put the four dates in your calendar with a reminder a week before each.
Pay online. Federal payments can be made directly and it takes minutes.
Do not forget your state. Most states with income tax have their own estimated payment system and their own dates.
If you are already behind
Pay what you can as soon as you can. Penalties are generally calculated on how much was unpaid and for how long, so a late payment is meaningfully better than waiting for April.
Then talk to a CPA about the current year rather than agonising over the last one. This is an ordinary situation and it has an ordinary fix.
What this article deliberately does not do
It does not tell you whether you owe estimated payments, how much, or what your rate is. Those depend on your whole tax picture.
What it does is make sure the system's existence is not the thing you discover in April.