Last updated: August 2026 | Tax year 2026/27
If you’re employed, someone usually makes this decision for you. Auto-enrolment quietly puts a slice of your pay into a workplace pension before you’ve thought about it, and whatever’s left over might drift into an ISA if you’re disciplined. Self-employed, that scaffolding disappears. No employer contribution, no default, no one nudging you. Just two account types — a SIPP and an ISA — and a decision you have to make deliberately, usually for the first time.
This isn’t personal financial advice — it’s a walk through how the two accounts actually work, so you can make an informed call for your own situation. If your circumstances are complex (multiple income sources, a limited company, or you’re close to retirement), it’s worth speaking to a regulated financial adviser before committing large sums.
The two accounts, in plain terms
A SIPP (Self-Invested Personal Pension) is a pension wrapper. Money you put in gets topped up with tax relief at your marginal rate — put in £80 as a basic-rate taxpayer and HMRC adds £20, taking it to £100. Higher and additional-rate taxpayers can claim further relief through Self Assessment. In exchange, the money is locked away until at least age 55, rising to 57 from April 2028. When you eventually draw on it, 25% typically comes out tax-free and the rest is taxed as income.
A Stocks and Shares ISA is an investment wrapper with no tax relief on the way in, but nothing is taxed on the way out either — growth, dividends, and withdrawals are all tax-free, and you can access the money at any age, for any reason.
The 2026/27 numbers:
- SIPP annual allowance: £60,000, or 100% of your relevant UK earnings if that’s lower — this covers all pension contributions combined, from any source
- ISA allowance: £20,000, across all ISA types combined
These two allowances are entirely separate. In principle, you could use both in full in the same tax year, though few self-employed people are anywhere near either limit.
Why the “which first” question matters more when you’re self-employed
For an employee, the pension question is partly answered by employer matching — free money you’d be leaving on the table by skipping it. Self-employed, there’s no match, so the SIPP’s advantage narrows down to one thing: the tax relief itself, weighed against losing access to the money for decades.
That trade-off changes the calculation quite a bit, and it interacts with a few things that are specific to self-employment.
1. Income volatility
Employees plan around a predictable payslip. Self-employed income can swing wildly month to month or year to year. Locking money into a SIPP works well in a strong year, but it means that money is unavailable if next year is lean and you need a buffer. An ISA is more forgiving here — the money’s still invested, still working, but it’s there if you genuinely need it.
A reasonable approach many self-employed people land on: build a cash buffer first (three to six months of essential costs), then split ongoing surplus between ISA and SIPP rather than going all-in on one.
2. The tax relief case is strongest against your highest tax band
Because relief is applied at your marginal rate, a SIPP contribution is most valuable in a year when you’re a higher or additional-rate taxpayer, and least valuable in a lean year when you’re barely above the personal allowance. Self-employed income often varies enough year to year that timing contributions around your tax band — contributing more into a SIPP in a strong year, leaning on the ISA in a quieter one — can meaningfully change how much relief you actually capture.
3. Carry forward is a genuine self-employed advantage
Unused pension annual allowance can be carried forward from the previous three tax years, provided you had relevant UK earnings in those years. For someone whose income has just picked up after a slower stretch, this can allow a much larger SIPP contribution — and a correspondingly larger tax relief claim — than the standard £60,000 figure suggests. The ISA allowance has no such carry-forward: unused allowance is simply lost at the end of each tax year.
4. Limited company directors have a third option
If you trade through a limited company rather than as a sole trader, the company itself can make pension contributions directly on your behalf, as an allowable business expense — separate from, and in addition to, anything you contribute personally. This is worth its own dedicated look (coming shortly), but it’s a meaningful reason the “SIPP vs ISA” question can play out differently depending on how your business is structured.
A rough framework, not a rule
There’s no single right order — it depends on your tax band, how stable your income is, and how far off retirement you are — but a few starting principles come up often:
- No cash buffer yet? Build that before committing meaningfully to either.
- Higher-rate taxpayer this year? The tax relief on a SIPP contribution is doing more work for you right now than it will in a lower-earning year — worth weighting SIPP contributions toward strong years.
- Value flexibility, or years from retirement age? The ISA’s any-time access makes it the more forgiving home for money you might plausibly need before you’re 55-57.
- Already got a cash buffer and steady income? Splitting new contributions between both, rather than picking one exclusively, is how a lot of people land — it doesn’t have to be all-or-nothing.
What’s next
This is the first piece in a short series on investing and retirement planning for people without an employer pension behind them. Next up: how director’s pension contributions actually work if you trade through a limited company, and why it’s one of the most underused tax-efficient moves available to small business owners.
This article is for general information only and does not constitute financial advice. Tax rules can change, and how they apply depends on your individual circumstances. Where a product or provider is mentioned on this site, we may earn a commission — see our [editorial policy] for details.