The hardest part of self-employment usually isn't earning the money. It's that the money arrives in lumps while the rent, the direct debits and the food shop arrive monthly, and the single biggest bill of the year arrives in one hit at the end of January.

Most advice on this stops at "put some aside for tax". That is not a system, because it never says how much, and the honest answer is that the right percentage in your first year is nothing like the right percentage afterwards. This post works the real numbers through at the 2026/27 rates, sizes the pots properly, and sets out what to do if a quiet quarter means you cannot pay.

Pay yourself a wage, not a raid

The instinct is to spend what's in the account when a big invoice lands, then scramble through the quiet weeks. Reverse it. Decide a fixed monthly amount to transfer from your business account to your personal account — a business payday — and pay it on the same date every month whether it was a £9,000 month or a £900 one.

The business account absorbs the lumpiness. Your personal life gets a salary. And "can I afford this?" becomes an answerable question again, because your personal account finally has a predictable number in it.

Set the payday from your lowest plausible three-month average, not your best month. You can always take a top-up in a good quarter. Cutting your own wage in a bad one is how people end up on a credit card.

Three pots, and what actually goes in the tax one

Split every payment the moment it arrives:

  • Tax pot — moved out immediately. This money was never yours.
  • Buffer pot — building towards three months of fixed costs, business and personal combined.
  • Working pot — what's left funds the business payday and running costs.

The universal advice is 25–30% into the tax pot. That number is right, but almost everyone is right about it for the wrong reason — and the reason is what tells you when to change it.

Worked example — a freelancer's first two years, 2026/27 rates. The business figures are illustrative; every tax rate and threshold is the real one.

A freelancer's first full year is 2026/27: turnover £52,000, allowable costs £10,000, profit £42,000, and no other income.

The tax itself. The personal allowance is £12,570, so £29,430 is taxed at the 20% basic rate = £5,886. Class 4 National Insurance is 6% on profits between £12,570 and £50,270, so £29,430 × 6% = £1,765.80. Class 2 is treated as paid without payment, because profits are above the £7,105 small profits threshold. Total liability: £7,651.80 — which is 18.2% of profit, comfortably under the 25–30% everyone quotes.

Now the January that actually happens. The bill is over £1,000, so payments on account start. On 31 January 2028 this freelancer owes the £7,651.80 balancing payment plus a first payment on account of half that again, £3,825.90 — £11,477.70 in one go. A second £3,825.90 follows on 31 July 2028.

£11,477.70 is 27.3% of the year's profit. That is where 25–30% comes from. It is not your tax rate — it is the size of the first January.

Year two, steady state. If 2027/28 lands at the same £42,000, the two payments on account have already covered it, so 31 January 2029 asks only for the next first instalment: £3,825.90. Across that calendar year you pay £7,651.80 — back to 18.2%.

So the rule is: set aside 30% until your first January is behind you, then recalculate against your actual liability. Keeping 30% forever is not prudent, it is an interest-free loan to a savings account. Dropping to 18% in year one is how people end up short by four figures.

Two adjustments. If your profits cross £50,270, the marginal rate jumps to 40% income tax plus 2% Class 4, so anything above that line needs 42% set aside, not 26%. And if you are VAT registered, VAT is a fourth pot entirely — it was never your money for a moment.

A Mettle account makes the split a ten-second job with in-app pots, and FreeAgent shows the live tax estimate as the year runs, so the pot tracks the real figure rather than a guess.

Size the buffer from your floor, not your average

Three months of fixed costs is the target, and "fixed costs" means everything that arrives whether you work or not: rent or mortgage, utilities, insurance, subscriptions, software, and the business payday itself. Add them up once, multiply by three, and that is the buffer's finish line.

It is not an emergency fund. It is the thing that lets you turn down a bad-fit client at a bad-rate in a slow month — which, over a year, is usually worth more than the buffer itself.

Forecast the dips you already know are coming

Freelance income has a rhythm. Quiet Augusts, dead fortnight at Christmas, a retainer that ends in Q3, a client who always pays 45 days late. You generally know where the gaps fall; what's missing is writing them down.

A single sheet with the next six months across the top, expected receipts and fixed costs down the side, and a running balance at the bottom is enough. It converts a vague sense of dread into a specific date — and a specific date can be acted on. You line up work in advance, move a spend, or draw on the buffer deliberately.

From 6 April 2026, if your qualifying income was over £50,000, Making Tax Digital for Income Tax requires quarterly updates anyway — over £30,000 from April 2027 and over £20,000 from April 2028. Quarterly updates are much easier to see as an imposition than an opportunity, but they do force the forward look four times a year. Our post on quarterly updates with multiple income streams covers the mechanics.

When a quiet quarter means you cannot pay

This is the part of the problem nobody writes about, and there are three real options. Interest is the constant: HMRC charges late payment interest at 7.75% from 9 January 2026, set at the Bank of England base rate plus 4 percentage points, so it moves when the base rate does.

  1. Budget Payment Plan — pay ahead, by direct debit. If you are up to date with previous Self Assessment payments, you can set up weekly or monthly payments in advance towards your next bill. Payments are credited against it, you can pause for up to six months, and if you have overpaid you can ask for a refund. This is the tax pot, run by HMRC, for people who cannot leave a savings account alone.
  2. Time to Pay — spread a bill you already owe. If you owe up to £30,000, you can set this up online yourself within 60 days of the 31 January deadline and spread it over up to 12 months. You must have filed the return first, and wait 72 hours after filing before setting the plan up. Interest still runs at 7.75%, and missing a payment can bring the whole balance back at once. Above £30,000 or over a longer period, you phone HMRC.
  3. Reduce your payments on account — but honestly. If next year's income will genuinely be lower, you can apply to reduce the instalments online or on form SA303. Reduce too far and HMRC charges interest on the shortfall from the original due date. Optimism here is expensive.

All three are better than the fourth option, which is silence. The one thing that turns a cashflow problem into a penalty problem is not filing — file on time even if you cannot pay, because filing and paying are separate obligations with separate consequences.

Protect the essentials when costs climb

When money is tight the instinct is to cut what feels optional: pension contributions, insurance, the buffer. Those are usually the things protecting you. Better levers, in order:

  • Audit subscriptions. Software you signed up for during one project and never cancelled is the easiest money in the business.
  • Claim everything you are entitled to. Every legitimate expense you miss costs you 26p in the pound at basic rate and 42p at higher rate. Under-claiming is not caution, it is a donation.
  • Revisit your rates. A day rate held flat through an inflationary stretch is a pay cut you gave yourself. Our post on pricing your work has the method.

Do this in the next week

  1. Open a second account or pot and name it Tax. Not a mental note — an actual pot with a name.
  2. Set the percentage. 30% of every payment if your first January is still ahead of you; your real rate afterwards.
  3. Add up three months of fixed costs and write the number down. That is the buffer target.
  4. Pick a business payday date and a figure based on your worst recent quarter, then set the standing order.
  5. Diarise 31 January and 31 July. The tax calendar has the rest of the dates.

A named accountant who knows your numbers can tell you what to set aside, warn you what January looks like months before it arrives, and say whether your rates still stack up — part of every package from £19 + VAT a month. Irregular income is entirely manageable. It just needs a system instead of hope. Get started.