Money & Taxes
How do freelance taxes work?
Freelance tax mechanics differ by country, but the shape is the same everywhere: nobody withholds tax from your income for you, so you calculate and pay it yourself — usually in installments during the year, not just once at filing time. Below: how it works in the US (self-employment tax + quarterly estimated payments) and the UK (Self Assessment + payments on account), including why UK freelancers often get billed twice in one go.
Freelance taxes work differently depending on where you're based, but the underlying problem is universal: as a freelancer you're your own payroll department. No employer withholds income tax or Social Security/National Insurance from what clients pay you, so you're responsible for setting money aside and paying it in on a schedule the tax authority sets — not whenever it's convenient. The two sections below cover the US and UK specifically, since the mechanics (and the confusing bits) differ.
How does self-employment tax work in the US?
Self-employment tax is a flat 15.3% tax covering Social Security (12.4%) and Medicare (2.9%), applied to 92.35% of your net self-employment earnings, and it's separate from — and in addition to — ordinary federal income tax. It exists because a traditional employee and employer each pay half of these payroll taxes normally; as a freelancer, you're both, so you pay the full 15.3% yourself. You owe self-employment tax once your net earnings from self-employment hit $400 in a year, and you calculate it on Schedule SE, filed with your Form 1040.
On top of self-employment tax, your freelance profit is also subject to ordinary federal income tax at your regular bracket rate, and possibly state income tax depending on where you live. That's why freelancers often end up owing noticeably more than a W-2 employee earning the same gross amount — it isn't one tax, it's two stacked on top of each other. Check irs.gov's Topic 554 for the current-year specifics, since the Social Security wage base cap adjusts annually.
How do quarterly estimated tax payments work in the US?
If you expect to owe $1,000 or more in tax for the year after withholding and credits, the IRS generally expects that tax paid throughout the year in quarterly installments, not as one lump sum when you file. This applies whether the $1,000 comes from self-employment tax, income tax on freelance profit, or both combined. Missing a quarter isn't just a timing problem — the IRS can charge an underpayment penalty for the period you were behind, calculated similarly to interest on the shortfall.
Estimated payments are made using Form 1040-ES, and the IRS's safe-harbor guidance gives you a target that avoids the penalty even if your actual final bill is higher: pay in, across the year, the lesser of a set percentage of your current-year liability or your prior-year liability (a higher percentage applies if your prior-year income was above a set threshold). The exact percentages and dollar thresholds are adjusted periodically, so confirm the current figures at irs.gov's estimated tax guide rather than relying on a fixed number here.
What is UK Self Assessment?
Self Assessment is HMRC's system for reporting income that isn't taxed automatically through payroll — the standard route for anyone who's self-employed or freelance in the UK. If you're newly self-employed you need to register for Self Assessment (the registration deadline is 5 October following the tax year you started trading), after which HMRC sends you a Unique Taxpayer Reference and you file a return each year reporting your income and expenses.
The filing and balancing-payment deadline is 31 January following the end of the tax year — file online and pay any Income Tax and Class 4 National Insurance owed by that date. Unlike the US, there's no separate self-employment-specific tax rate stacked on top of income tax; instead, Self Assessment calculates your Income Tax and National Insurance together based on your profit. Check gov.uk's Self Assessment payment overview for current deadlines and thresholds.
What are "payments on account" and why do they confuse freelancers?
Payments on account are advance payments toward next year's tax bill, charged alongside your balancing payment for the year you're actually filing — which is exactly why freelancers on r/selfemployed and elsewhere describe being confused about owing "two payments" out of nowhere. Each payment on account is normally half of what you owed the previous year, due in two installments: 31 January (alongside your balancing payment for the prior year) and 31 July.
So a first-time Self Assessment filer can hit 31 January owing three things at once: the balancing payment for the year just finished, plus the first payment on account toward the year that's still in progress — effectively 150% of one year's tax bill in a single payment, with a second installment (another 50%) due the following July. That's the "why did I have to pay twice" moment: it isn't a mistake or a double charge, it's HMRC collecting next year's tax in advance because it has no employer withholding to rely on for freelancers. You're exempt from payments on account if last year's tax bill was under £1,000, or if more than 80% of what you owed was already collected some other way (e.g. through a tax code). If you know this year's profit will be lower than last year's, you can ask HMRC to reduce your payments on account — but if you reduce them too far and your actual bill comes in higher, HMRC can charge interest on the shortfall. See gov.uk's payments on account guide for the mechanics.
US vs UK: what's actually different?
The core mechanic is the same on both sides of the Atlantic — no employer withholding, so you pay tax yourself on a schedule, not just once a year — but the shape of the schedule differs. The US spreads payments across four estimated-tax due dates roughly tied to the calendar year and calculates them off your own current-year forecast. The UK collects in two payments on account tied to the following 31 January/31 July, sized off last year's actual bill rather than a forecast, which is exactly what produces the "paying for a year you haven't finished yet" feeling new UK freelancers report. Neither system is charging you extra over the course of your freelance career — both eventually true up to what you actually owed — but the UK's advance-collection model front-loads more of the pain into your first year or two of trading.
Either way, the fix is the same: don't wait for the bill to tell you what to set aside. Track profit as it comes in and put a percentage aside per payment, rather than discovering the number in January.
How does self-employment tax work in the US?
Self-employment tax is a flat 15.3% (12.4% Social Security + 2.9% Medicare) applied to 92.35% of net self-employment earnings once those earnings reach $400 in a year, calculated on Schedule SE and filed with Form 1040 — separate from, and in addition to, ordinary federal income tax.
How do quarterly estimated tax payments work in the US?
If you expect to owe $1,000 or more in tax for the year, the IRS expects it paid across the year in quarterly installments via Form 1040-ES rather than as one lump sum at filing — missing a quarter can trigger an underpayment penalty even if you're owed a refund overall.
What is UK Self Assessment?
Self Assessment is HMRC's system for self-employed people to report income and pay Income Tax and Class 4 National Insurance that isn't collected through payroll, with registration due by 5 October after you start trading and filing/payment due by 31 January.
What are "payments on account" and why do they confuse freelancers?
Payments on account are advance installments toward next year's tax bill, each normally half of what you owed last year, due 31 January and 31 July — new filers are often surprised to owe a balancing payment plus the first payment on account (about 150% of one year's tax) at once. You're exempt if last year's bill was under £1,000 or 80%+ was already collected another way.
US vs UK: what's actually different?
Both systems replace employer withholding with self-paid installments, but the US spreads four estimated payments across the current year based on your own forecast, while the UK's two payments on account are sized off last year's actual bill and collected in advance — which is what creates the "paying for an unfinished year" feeling for new UK freelancers.