SIPP vs ISA: which is better for retirement?

SIPP vs ISA at a glance

SIPPs and ISAs are both "wrappers": accounts that can hold the same funds but are taxed differently. Both let your savings grow free of tax. The difference is when the tax is paid: a pension gives you tax back on the way in and taxes most of what comes out, while an ISA takes money you have already paid tax on and never taxes it again. A pension also locks the money until 55, rising to 57 from 6 April 2028. An ISA can be spent at any age.

A SIPP is a self-invested personal pension: a pension you open yourself and choose the investments in. It follows exactly the same tax rules as a workplace pension, so everything here applies to both. The fair comparison is with a stocks and shares ISA holding the same funds. A cash ISA is for money you need soon, not for retirement decades away.

Most people end up using both. The rest of this guide puts numbers on the trade-off: how much more a pension is worth at your tax band, the situations where an ISA wins, and how to split the two if you want to stop work before 57.

What £100 in a pension is worth at every tax band

Putting £100 into an ISA costs you £100 of take-home pay. Putting £100 into a pension costs less, because the income tax you paid on that money is handed back - and the higher your tax band, the more comes back. The catch is on the way out, where three-quarters of a pension withdrawal is taxed as income.

Non-taxpayers get relief too. Even with no earnings at all you can pay up to £2,880 a year into a pension and the provider adds £720, making £3,600. That makes a pension worth considering for a partner who is not working, as long as the money can stay put until 57.

The 60% band is the best deal of all. Between £100,000 and £125,140 you lose £1 of your tax-free personal allowance for every £2 of income above £100,000, so each extra £100 of salary is taxed at 60%. Paying that slice into a pension wins the allowance back: £100 in the pot costs £40. Above £125,140, relief is 45%.

How you claim matters. With a SIPP, your provider claims the first 20% from the government and adds it for you - this is called relief at source. Higher and additional-rate taxpayers claim the rest through a Self Assessment tax return or by contacting HMRC, and many never do. Salary sacrifice through a workplace scheme saves National Insurance as well, which is why its rows are cheaper still. From 6 April 2029, National Insurance will apply to sacrificed contributions above £2,000 a year, but the income tax relief stays.

Investment growth does not change the answer

Both wrappers grow free of tax on dividends, interest and capital gains, so the same fund in a SIPP and an ISA grows at exactly the same rate. Growth multiplies both pots equally, which means it cannot change which one ends ahead - only tax in, tax out and access can.

Take £300 a month of take-home pay for 20 years on our Balanced assumptions. In an ISA it becomes £88,629 in today's money. The same £300 pays £375 a month into a pension for a basic-rate taxpayer, which becomes £110,786 - and £94,168 once three-quarters of it has been taxed at 20%. Run the same sums at 3% or 7% growth and every figure moves, but the pension still ends 6% ahead.

You cannot beat an ISA by picking better funds inside a pension. Which wrapper wins comes down to tax and access; the funds are a separate decision, and you can hold the same ones in both.

So you do not need a growth forecast to make this choice, which is a relief, because growth is the assumption that moves every other retirement number the most. Where growth does matter is the size of the pot you need in total - and that is the same whichever wrapper it sits in.

When an ISA is the better choice

A pension's edge assumes you can leave the money alone until 57, that you will not pay more tax in retirement than you save now, and that the tax-free quarter is still there for you. An ISA comes out ahead in five situations.

• You might need the money before 57. A pension pound is locked until 57 from 6 April 2028. Redundancy or a house move will not unlock it; only serious ill health can. Keep an emergency fund, and money for anything you plan before then, in an ISA or savings. If you plan to retire early, the years before 57 have to be paid for from an ISA too - see the next section.
• You pay basic rate now but will pay higher rate in retirement. If your income in retirement will be over £50,270 - usually because of a large final salary pension or a very big pot - a pension pound saved at basic rate comes back as £70 for every £80 it cost. That is 13% worse than an ISA. (A higher-rate payer who also pays higher rate in retirement still gets £70 for £60, so the pension still wins for them.)
• Your pensions are heading past £1,073,100. Tax-free cash is capped at £268,275 across all your pensions for life, which is 25% of £1,073,100. Beyond that every pound comes out fully taxed, so basic-rate money gains 0% from a pension and is locked away for nothing. Higher-rate relief still makes a pension worthwhile; basic-rate saving is better off in an ISA.
• The money is meant for your family, not for you. Until 6 April 2027 unused pensions sit outside your estate, which made them the best way to pass money on. From that date they count towards it for inheritance tax, just as ISAs already do. On top of that, if you die at 75 or over, whoever inherits your pension pays income tax on what they take out; an inherited ISA has no income tax. For money you plan to spend yourself, nothing changes.
• You are under 40 and the money is for after 60. A Lifetime ISA adds 25% to up to £4,000 a year and pays out tax free from 60, so £4,000 becomes £5,000. The same £4,000 in a pension becomes £4,250 after tax at basic rate. It beats a basic-rate pension but loses to a higher-rate one (£5,667), and taking the money before 60 for anything but a first home costs a 25% charge. Lifetime ISA vs SIPP compares them in full.

Retiring before 57: why you need both

An early retirement has three stretches, and the two wrappers do different jobs in each. Before 57 only an ISA can pay for anything. Between 57 and your State Pension a pension is at its most tax-efficient. After that, the State Pension uses up your tax-free allowance and three-quarters of every pension pound is taxed on the way out.

The date that makes this urgent is 6 April 2028, when the normal minimum pension age rises from 55 to 57 with no phasing. Anyone born after 5 April 1973 cannot touch a private pension before 57 unless their scheme has a protected pension age. So retiring at 55 now needs two years paid for from outside a pension, and retiring at 50 needs seven.

Every year before 57 has to come from money with no age lock. At £2,200 a month that is £26,400 a year in today's money. The table shows what that adds up to, and how many years of a full £20,000 ISA allowance it takes to build.

The ISA is not extra money on top of the pot you need. It is part of the same total, held in the wrapper you can reach. Stopping at 55 needs about £513,000 in all on these assumptions, of which £52,800 - 10% - has to be outside a pension. Stopping at 50 pushes that share to 31%, which is why very early retirements are built mostly in ISAs, whatever the tax relief says.

Two things soften the table. Some of the money can sit in ordinary savings or a general investment account rather than an ISA - it is the age lock that matters, not the wrapper - though outside an ISA you pay tax on interest, dividends and gains. And any earnings before 57, even a day or two a week, shrink the amount you need faster than anything else on this page.

Which to spend first: the pension or the ISA?

Usually the pension, as soon as you can reach it. Between 57 and your State Pension age you may have no other income, so your £12,570 personal allowance is sitting unused. Taken as lump sums that are 25% tax free and 75% taxable, £16,760 a year comes out of a pension with no tax at all - because three-quarters of it is exactly £12,570.

Once the State Pension starts, that allowance is mostly gone. The full new State Pension is £12,548 a year in 2026/27, which leaves just £22 of the allowance for anything else. From then on every pension withdrawal loses 15% on the way out. The same pound of pension is worth £1.00 drawn before your State Pension and £0.85 drawn after it.

The first row is not as bad as it looks: the tax on drawing more than £16,760 a year is the same whether you pay it now or later. The real waste is the third row.

This flips the way most people think about the two. Most people spend the ISA first because it is flexible. Do the opposite. The ISA pays for the years before 57, then fills the gap above £16,760 a year, and then keeps growing tax free long after the pension has been taxed. How long a given pot lasts is a separate question, and the answer is the same whichever wrapper it sits in.

Where the next pound goes, in order

Put the tax facts and the access rules together and a clear order falls out. Work down the list until you run out of pounds - and if you are not sure how many you have, the disposable income calculator counts them from your salary and essential bills.

1. 1An emergency fund you can reachA few months of spending in an easy-access savings account or cash ISA comes before any long-term saving, so a surprise bill never forces you to sell investments at a bad moment.
2. 2Every pound your employer will matchIf your employer matches what you pay in, up to a limit, each matched pound is an instant 100% return before any tax relief, and no ISA can compete with that. If your scheme matches up to a percentage of salary, pay in at least that much.
3. 3The ISA bridge, if you plan to stop before 57Count the years before 57, multiply by a year of spending, and build that in an ISA first - £52,800 for a stop at 55 on £2,200 a month. The tax relief you give up is the price of being able to stop on the day you choose. If the bridge is bigger than £20,000 a year can build in the time you have, the answer is a later stop date, or topping up the bridge from a general investment account.
4. 4The pension, for every pound of income taxed at 40% or moreA higher-rate taxpayer gets 42% more per pound from a pension than an ISA if they pay basic rate in retirement, and 47% more through salary sacrifice. In the 60% band above £100,000 the edge is 113%, and at additional rate it is 55%. Higher relief only applies to income actually taxed at the higher rate, so keep going until that slice is used up.
5. 5The pension for basic-rate taxpayers too, once the bridge is fundedThe edge is smaller - 6% with relief at source, 18% through salary sacrifice, and 25% on anything you can draw inside the personal allowance before your State Pension - but it is still an edge, and it compounds for decades. A non-taxpayer gets the same basic-rate relief on up to £2,880 a year. A workable rule: pension for money you are sure is for retirement, ISA for money you might need first. Under 40, a Lifetime ISA is worth a look for some of it.
6. 6Whatever is left goes wherever there is still roomThe pension annual allowance is £60,000 a year including employer contributions and tax relief, and the ISA allowance is £20,000. Few people fill both. If you do, a general investment account is next: it has no limits, but its interest, dividends and gains are taxed.

Three savers, three splits

The order above gives very different splits depending on the stop date and the tax band. All three are aiming at £2,200 a month, already take their full employer match, and are deciding where the next pound of their own money goes.

The rules that can tip the balance

The per-pound maths is the same for everyone. These are the limits and exceptions that change it for some people.

• The annual allowance is £60,000. That is the most that can go into pensions in a tax year with tax relief, counting your contributions, your employer's and the relief itself. It is lower for very high earners, and unused allowance from the previous three years can usually be carried forward. Your own contributions only get relief up to your earnings for the year.
• Taking taxable money from a pension cuts the allowance to £10,000. This "money purchase annual allowance" applies for good once you take taxable money from a pot-of-money (defined contribution) pension. It catches early retirees who go back to work: drawing at 57 and earning again at 60 leaves little room to rebuild. Taking only your tax-free cash, with nothing taxable, does not trigger it.
• Tax-free cash is capped at £268,275. That is 25% of £1,073,100, across all your pensions. Above that, basic-rate money is better off in an ISA.
• Pensions join your estate for inheritance tax from 6 April 2027. The first £325,000 of an estate is tax free (more if your home passes to children or grandchildren, and anything left to a husband, wife or civil partner is exempt), and the rest is taxed at 40%. That removes the advantage pensions had over ISAs for money you never expected to spend.
• Salary sacrifice above £2,000 a year will pay National Insurance from 6 April 2029. The income tax relief is unaffected, so the salary sacrifice rows above shrink towards the ordinary pension rows for larger contributions.
• Scotland taxes income differently. Scottish rates and bands differ, with a lower starter rate and higher rates further up, so the relief on the way in and the tax on the way out both move. Relief at source still adds 20% for everyone. The order of the steps stays the same; the size of the pension's edge changes.

What this comparison leaves out

Tax rules are the one part of a forty-year plan that is certain to change. Treat the edge figures as today's answer, not a promise.

• Future tax rates. Every figure assumes 2026/27 rates on the way out as well as in. The 25% tax-free lump sum, the personal allowance and the basic rate have all been the subject of Budget speculation, and any of them moving changes the pension's edge - though not the access rules.
• Frozen allowances. The personal allowance is frozen while the State Pension rises. The full State Pension is already within £22.40 of the allowance and is likely to pass it, after which every taxable pound you draw after State Pension age is taxed.
• Final salary pensions. If you have one, keep it. It pays a guaranteed income, and transferring it into a SIPP rarely pays off. Count it as income and use this guide for the rest of your savings.
• Fees. All the figures assume the same charges in both. A workplace scheme with a low negotiated fee, or a SIPP charging 1% a year, can be worth more than the 6% basic-rate edge over a long enough time.
• Benefits, Child Benefit and student loans. Pension contributions can lower the income used for Universal Credit and the High Income Child Benefit Charge; ISA contributions do not. Student loan repayments only fall if you pay in by salary sacrifice. For some people that outweighs everything else here.

None of that changes the shape of the answer. Money you might need before 57 has to sit somewhere without an age lock; everything after that is a tax question, and pensions usually win tax questions. What the total pot has to be is the bigger number, and the split is how you make sure you can spend it.

How to decide for yourself

Frequently asked questions