Should you invest in a pension or an ISA? Is there a decisive answer to the eternal SIPPs vs ISAs question?
Well… almost. We can make a few immediate statements that provide clear direction – although the decision tree gets pretty thorny after that:
- If you hope to live off your investments before your minimum pension age1 then a stocks and shares ISA is the clear winner.
- Employer pension contributions are an unbeatable leg up. Take them, take them, take them. It’s free money, unless you plan on dying a rock ‘n’ roll death. (Pro tip: almost nobody does.)
Otherwise, much depends upon if you’re contributing to your SIPP (or other pension type) at the higher-rate of income tax or at the basic rate:
- Paying higher-rate tax? Then prioritise your pension accounts over ISAs.
- Paying basic-rate tax? Then the choice between a SIPP and a Lifetime ISA (LISA) is finely poised. We delve deeper into this below.
- If you’re a young basic-rate taxpayer who won’t retire until State Pension age, an ISA may beat a SIPP in certain scenarios. Again, we’ll explain more below.
The Kong-sized caveat to all this is that future changes to the tax system may move the SIPP vs ISA goalposts.
Goalposts on wheels
Tax-strategy diversification can help you address the uncertainty. It involves you employing several different tax shelters, irrespective of their current pecking order.
Spreading your savings across various tax shelters is particularly sensible for young people for whom retirement is decades away. But the technique is worth everyone else considering too, because SIPPs and ISAs hedge against different tax risks. We’ll talk about that in a sec.
To set the scene, let’s first recap what ISAs and SIPPs have in common – and what sets them apart.
Terminology intermission: I mostly talk about SIPPs in this article but the conclusions apply equally well to other defined contribution (DC) pensions, such as Nest-style auto-enrolment Master Trust Pensions. I’ll use the term ISAs to refer to all ISA types, except for the LISA. I’ll mention the LISA when its special features alter the SIPP vs ISA comparison.
SIPPs vs ISAs: these things are the same
SIPP or ISA? There’s nothing between them on the following counts:
Tax shelter / feature | SIPP | Stocks and shares ISA |
No tax on dividends | Yes | Yes |
No tax on interest | Yes | Yes |
No tax on capital gains | Yes | Yes |
Invest in funds, ETFs, bonds, shares | Yes | Yes |
Ceiling on lifetime tax-free income | No | No |
Versions for children | Yes | Yes |
SIPPs vs ISAs: these things are different
ISA or SIPP? Well, on the other hand…
Tax shelter / feature | SIPP | Stocks and shares ISA |
Free of income tax on withdrawals | No | Yes |
Income tax relief on contributions | Yes | No |
Tax relief on National Insurance | Yes, with salary sacrifice | No |
25% tax-free cash on withdrawal | Yes, up to £268,275 | N/A |
Access anytime | No | Yes |
Annual limit on contributions | £60,000 | £20,000 |
Employer contributions | Yes | No |
Inheritance tax exempt | Only until April 2027. Fine if passed to spouse | If passed to spouse, otherwise no |
As you can see, a SIPP gathers more ‘Yes’ votes than an ISA.
Those advantages stack up.
ISAs are superior to SIPPs when access to your money before the normal minimum pension age is your top priority.
However, the various pension tax breaks on offer combine to make SIPPs the best option for the bulk of most people’s retirement savings.
LISAs are a different kettle of tax wrapper. Their dream combination of tax relief and tax-free withdrawals make LISAs an attractive option for basic-rate taxpayers vs pensions – under some circumstances.
The devil is in the detail and we’ll dance with him shortly. Before that, let’s talk tax-strategy diversification.
Tax-strategy diversification in retirement planning
Tax-strategy diversification for UK investors means spreading your retirement savings between your LISA, ISA, and SIPP accounts. It’s a defence against adverse changes to the tax system in the future.
The concept is analysed in a US research paper called Tax Uncertainty and Retirement Savings Diversification by Brown et al.
The paper examines the impact of tax code changes upon the traditional IRA and the Roth IRA. These two American tax shelters are analogues of our SIPP and ISA, respectively.
The authors make several key observations. I’ve translated their US tax-shelter language directly into their UK equivalents, as follows…
SIPPs are negatively affected by income tax hikes in the future. They are positively affected by income tax falls.
For example, if you get tax relief at 20% now but are later taxed on retirement withdrawals at 22% then that’s a blow against pensions.
The reverse is true for ISAs. They’re taxed upfront and so enable you to lock in your income tax rate now. This is an advantage for ISAs vs SIPPs if tax rates rise in your retirement.
For example, you win if you took a 20% tax hit on the salary that funds your ISA contributions today but then the basic rate of tax rises above 20% by the time you come to withdraw tax-free in the future.
Meanwhile SIPPs offer a hedge against poor pension performance. If your investments are hit by a terrible sequence of returns then more of your withdrawals will probably be taxed at a lower tax bracket. This offsets some of the damage wreaked by bad luck, especially if you banked higher-rate tax reliefs when you were working.
The long game
The whole research paper is worth a read. But the following quotes provide particular insight on how future tax changes could boost or hobble SIPPs and ISAs for different demographics.
Future tax rates are more uncertain over longer retirement horizons. Our analysis of historical tax changes also suggests that the rates associated with higher incomes are more variable.
The paper’s authors found that income tax rates were much more volatile for high earners going back to 1913…
…as a result, the highest tax-risk exposures will occur among younger investors with sufficient traditional account [such as SIPP] savings to produce taxable income in retirement that exhausts the lower-income brackets. Young, high-income investors who are likely to meet these criteria can manage their exposure to tax-schedule uncertainty by investing a portion of their wealth in Roth [for us, ISA] accounts.
High-income investors increase their allocations to Roth [ISA] accounts when faced with uncertainty about future tax rates. At these income levels, reducing consumption risk in retirement by locking in tax rates today is more valuable than realizing a potentially lower tax bracket in the future.
(Our pointers are in italics).
Young, higher-earners are the most susceptible to steep future tax rises, according to this analysis. Tax-strategy diversification implies that they should hedge against that possible fate by ploughing a significant portion of today’s income into ISAs. The danger with SIPPs is that future withdrawals may be made at tax rates that are higher than the reliefs on offer today.
I’d caution, though, that the biggest SIPP vs ISA gains come from taking higher rates of tax relief on pensions that are subsequently taxed at a retiree’s much lower income tax rate. UK income taxes would have to rocket in the future to negate this advantage.
On the other hand, here’s a reason to invest in pensions that most of us would rather not think about:
Investors with sufficiently high current income must pay the top tax rate in the current period, however, such that the traditional [SIPP] account is preferable for higher-income investors who may end up in a lower tax bracket if the stock market performs poorly.
Eek. Well, bad things can happen.
The case for a bit of both
Ultimately the paper comes to a conclusion that I suspect many investors reach using their gut:
The optimal asset location policy for most households involves diversifying between traditional [SIPP] and Roth [ISA] vehicles.
Spreading your bets makes sense (as ever), especially when retirement is a dim and distant prospect.
But that said, do bear in mind this is a US-focused study. Their income tax bands are more incremental than ours.
In contrast, our SIPPs benefit from a massive cliff-edge if you enjoy higher-rate tax relief when you pay in but your retirement income falls mostly in the 0-20% band.
This feature of the UK tax system tilts the playing field heavily in favour of pensions vs ISAs, as we’ll see.
(Note: I’ve used UK income tax rates throughout the article. The maths does change a little for Scottish taxpayers. While the broad conclusions are the same, the pecking order may change at the margins.)
ISA vs SIPP: when it doesn’t matter
You’re taxed upfront on money that goes into your ISA, but your withdrawals are tax-free.
SIPPs work the other way around. You pay less tax on contributions, but are subject to tax on money taken out. Thus UK pension vehicles can be thought of as tax-deferred accounts.
ISAs vs SIPPs is a dead heat when the tax deducted from your ISA contributions matches the tax you pay on pension withdrawals.
The amount of cash you can take out of each account is exactly the same in this situation, as shown in the following example:
Account | Gross income | Net after tax | After tax relief | Withdrawal |
ISA | £100 | £80 | £80 | £80 |
SIPP | £100 | £80 | £100 | £80 |
The example tracks the value of £100 through the tax shelter journey, from contribution to withdrawal.
Think of it as comparing each £100 that you could choose to put in either your ISA or SIPP.
- Gross income is earned before tax.
- Net after tax is the amount left in your account after HMRC takes its bite.
- After tax relief is the value of your savings after any rebates.
- Withdrawal is what’s left of your original £100 once taken in retirement (based on current tax rates and ignoring investment returns because they’re ISA vs SIPP neutral).
A previous post of ours walks you through the underlying SIPP vs ISA maths.
But just to be clear, pensions always win when an employer contribution match is on the table.
Pound-for-pound an employer match doubles your money. Not taking the match is like volunteering for a pay cut.
Same difference
Employer contributions notwithstanding, the example above shows that the tax-saving powers of an ISA or a SIPP are evenly matched when:
- You’re taxed at 20% on the ISA cash you put in, and
- You’re taxed at 20% on the SIPP cash you withdraw
The amount of income you can take from each vehicle is the same, if the tax rates are equal. The order of tax and tax relief makes no difference to your investment returns, as The Investor has previously shown.
If both accounts gain, for example, 5% a year, then your SIPP’s balance will be larger than your ISA’s because there’s a bigger sum of money to grow after tax relief.
But the SIPP’s advantage is cancelled out by tax on withdrawal. Hence the Withdrawal value is identical for both accounts in this scenario.
If that’s the case for you then we need to head into an ISAs vs SIPPs tie-breaker situation.
ISAs vs SIPPs: tie-breaker situation
Priority | ISA | SIPP |
Access before pension age | Yes | No |
Inheritance tax benefit | Spouse | Spouse2 |
Means-testing / bankruptcy advantage | No | Yes |
Tax-strategy diversification | Use | both |
Personally, if I was many years from retirement I’d favour the accessibility of ISAs as a handy backstop. Just in case life took an unpleasant turn.
However the wisdom of tax-strategy diversification still suggests splitting your savings between both vehicles.
SIPPs vs ISAs: back in the real world
Because most people will be taxed at a lower rate of tax as retirees than they are as worker bees3, in practice pensions usually beat ISAs for retirement purposes.
Albeit LISAs are the wild card that can disrupt the SIPP vs ISA hierarchy.
Much depends on:
- How much 0% taxed cash4 your SIPP ultimately provides as a percentage of your retirement income.
- Whether your SIPP income is taxed at a lower bracket in retirement relative to the tax relief you snaffled while working.
To unpick the complexity, I’ll try to find the best-fit tax shelters for most people by running through some common retirement income scenarios.
I’ll account for variations in individual circumstances by looking at key breakpoints that alter the ISA vs SIPP rankings.
Breakpoint 1: the tax shelter types available
I tested the tax efficiency of four kinds of accounts that are useful for retirement savings:
Salary-sacrifice SIPP – this wrapper enables basic-rate employees to legitimately avoid 28% tax (20% + 8% NICs) while higher-rate employees avoid 42% tax (40% + 2% NICs)
SIPP – a standard pension account provides tax relief at the 20%, 40%, and 45% rates but you still pay national insurance contributions (NICs)
Stocks and shares ISAs – can deliver the investment growth needed for retirement.
As can LISAs – they also accept investments.
Breakpoint 2: retirement income levels and stealth taxes
I’ve examined three retirement income levels that align with the research published in the Retirement Living Standards report.
These three tiers equate to a Minimum, Moderate, and Comfortable living standard in retirement.
However, I’ve adjusted the incomes to account for our current era of stealth taxes.
The UK’s tax thresholds are frozen until April 2028. That is a tax hike by any other name.
The Office for Budget Responsibility estimates this manoeuvre amounts to increasing the basic rate of income tax from 20% to 24%.
Rising tax rates disadvantage pensions vs ISAs as noted earlier. So I’ve inflated the three retirement income levels by 2024-25 annual CPIH plus 3% assumed inflation for every year until 2028. This increased income requirement models SIPP withdrawals losing more to tax, as inflation erodes the lower brackets.
I assume that the tax thresholds rise with inflation after April 2028, as they should.
Breakpoint 3: how you use your personal allowance
The less your SIPP income is taxed in retirement, the better SIPPs do versus ISAs.
If you retire at age 55 and don’t receive a State Pension until age 67 then your SIPP’s tax performance improves – especially at lower retirement incomes – because a significant chunk falls into your personal allowance.
But the SIPP advantage contracts if your personal allowance is mopped up by the State Pension, defined benefit pensions, or by any other income.
Indeed, with the personal allowance frozen and the Triple Lock intact, the full State Pension could grow large enough to entirely fill the 0% income tax band by April 2028, or soon thereafter.
I’ve used that assumption in the examples below to guide anyone who thinks they’ll retire at State Pension age, or with a substantial source of alternative income.
Even if you retire early, the State Pension will arrive around ten years after your normal minimum pension age, from April 2028.
I account for this by modelling a 40-year retirement journey. This sees SIPP income cease to benefit from the personal allowance after the first decade.
Breakpoint 4: the fate of 25% tax-free cash
UK pensions are boosted by another blessed benefit. That’s the 25% tax-free cash that can be taken as a lump sum (known as the PCLS) or in ongoing slices as part of phased drawdown.
Before the Lifetime Allowance was abolished, the tax-free sum used to automatically reduce a basic-rate payers overall income tax burden from 20% to 15%.
But that can no longer be taken for granted – because the 25% tax-free cash allowance is now capped at £268,275.
It sounds a lot as of today, but the Chancellor has said the limit is frozen.
- Frozen until April 2028 – after which it rises with inflation?
- Frozen forever? In which case inflation will eventually swallow it like light quaffed by a black hole.
It’s not clear, so I’ve tested both scenarios.
The first scenario is relevant to near-term retirees who can assume their tax-free cash allowance will retain most of its current value when they retire. Especially if they’re at the Minimal to Moderate income levels and inflation is tamed again (which helps if the cap doesn’t rise in future years).
The second scenario may make sense if you’re three or four decades from retirement, and the cap remains frozen in time while inflation crushes it.
Right, let’s get on with our key ISA vs SIPP case studies!
SIPPs vs ISAs: £15,842 Minimum annual retirement income
In this example, SIPP contributions are made at the basic income tax rate and the 25% tax-free cash cap is not reached during a 40-year retirement.
Ranking | PA5 intact | Retire on State Pension | 40-yr retirement |
1. | Salary sacrifice | LISA | LISA |
2. | LISA / SIPP | Salary sacrifice | Salary sacrifice |
3. | – | SIPP | SIPP |
4. | ISA | ISA | ISA |
- PA intact = SIPP income benefits from the 0% personal allowance (PA)
- Retire on State Pension = SIPP income does not benefit from the personal allowance
- 40-yr retirement = The ranking for a 40-year retirement journey where the personal allowance is available to your SIPP for the first decade, while the State Pension absorbs the PA thereafter. 25% tax-free cash may run out at some stage. (Though not at the Minimum income level)
The headline is that a LISA wins across a 40-year retirement journey. The salary sacrifice pension used to win this category when we’ve previously run the numbers. But the reduction in National Insurance Contributions means that the LISA edges the contest now.
You can’t access a LISA until age 60 though, whereas it’s age 57 for most SIPP-owners from April 2028.
The LISA also now beats a salary sacrifice SIPP if you retire later with a full State Pension at age 67 (and/or a decent defined benefit pension et cetera).
A normal SIPP (‘relief at source’ or ‘net pay’, no salary sacrifice option) lags behind a LISA overall. Standard ISAs come last.
Despite this outcome, remember any pension is immediately catapulted above a LISA when your employer matches your contributions.
After you’ve trousered your employer’s contributions, you’re best off stuffing your LISA up to its £4,000 annual hilt on tax-strategy diversification grounds.
LISA contributions locked in at today’s tax rates will benefit versus pensions if taxes go up in the future (which they are doing until April 2028 at least, due to that infernal fiscal drag).
Basic-ally no difference
Intriguingly, a normal SIPP isn’t that far ahead of an ISA if you retire at State Pension age in this basic-rate taxpayer scenario.
You pocket £77 from a SIPP, and £72 from an ISA, for every £100 you originally contributed to each account. That’s a 7% difference.
Such a slim margin suggests that diversifying between the two accounts is a sound idea. Albeit I’d still heavily favour my SIPP, given that small gains make all the difference at lower incomes.
If the 25% tax-free cash is eliminated
Ranking | PA intact | Retire on State Pension | 40-yr retirement |
1. | Salary sacrifice | LISA | LISA |
2. | LISA | Salary sacrifice | Salary sacrifice |
3. | SIPP | ISA / SIPP | SIPP |
4. | ISA | – | ISA |
This scenario downgrades pensions, which means a LISA should take priority before you load up your pension.
For those retiring at the State Pension age, an ISA strategy even draws level with a non-salary sacrifice SIPP in terms of withdrawal value: £72 a piece for every £100 contributed.
If I really believed that the 25% tax-free cash benefit was set to whither to nothing then I’d overwhelmingly favour my ISAs vs SIPPs in this scenario.
However I think it’s more realistic to assume that the 25% tax break will retain some residual value, even if you’re 30-40 years away from retiring.
SIPP contributions made at higher-rate taxpayer level
Ranking | PA intact | Retire on State Pension | 40-yr retirement |
1. | Salary sacrifice | Salary sacrifice | Salary sacrifice |
2. | SIPP | SIPP | SIPP |
3. | LISA | LISA | LISA |
4. | ISA | ISA | ISA |
Higher-rate taxpayer contributions lead to a decisive win for pensions in the SIPPs vs ISAs match-up.
LISAs and ISAs form the bottom half of the table in this scenario and stay there.
Salary sacrifice and normal SIPPs continue to beat the L/ISA gang whether you retire at the Minimum, Moderate, or Comfortable income level.
However, if you expect tax-free cash to be disappeared by government chicanery then the LISA draws level with the SIPP at the £47,000 retirement income mark.
At £56,000 LISAs draw level with the salary sacrifice pension and are the best choice for investors who expect to rock a £61,000 retirement income.
Essentially, exposure to greater levels of higher-rate tax, and the loss of tax-free cash, knock the gloss of the SIPP relative to the LISA’s tax-free withdrawals.
LISAs also tie with salary sacrifice SIPPs at the £86,000 retirement income level even when you do have tax-free cash. That’s because you hit the lifetime tax-free cash cap so quickly.
But again, none of this undoes the primacy of pensions pumped up by employer contributions.
For those of us operating below such Olympian heights, the higher-rate tax reliefs are the sweet spot for pension contributions – because 40%-tax workers are likely to become 20%-tax retirees.
SIPPs vs ISAs: £34,435 Moderate annual retirement income
LISA is the way to go again if you’re making contributions at the basic income tax rate:
Ranking | PA intact | Retire on State Pension | 40-yr retirement |
1. | Salary sacrifice | LISA | LISA |
2. | LISA | Salary sacrifice | Salary sacrifice |
3. | SIPP | SIPP | SIPP |
4. | ISA | ISA | ISA |
Salary sacrifice’s lead over a LISA (in the left-hand column) is slight, even when you’re able to protect some withdrawals via your 0% tax personal allowance.
The principle of tax-strategy diversification suggests you’d do well to fill the LISA first.
Salary sacrifice outcomes continue to dominate normal SIPPs. That’s because they effectively gain relief on 32% tax, instead of 20%.
Meanwhile normal SIPPs enable you to withdraw 7% more than ISAs across a 40-year retirement, or if you retire at State Pension age.
If the 25% tax-free cash is eliminated
Ranking | PA intact | Retire on State Pension | 40-yr retirement |
1. | LISA | LISA | LISA |
2. | Salary sacrifice | Salary sacrifice | Salary sacrifice |
3. | SIPP | ISA / SIPP | SIPP |
4. | ISA | – | ISA |
The ISA / SIPP draw occurs because the SIPP’s 20% tax relief on contributions is the same as the ISA’s 20% tax exemption on withdrawals.
The SIPP vs ISA rankings for higher-rate taxpayer contributions are the same as the Minimum income level, regardless of what happens to the 25% tax-free cash. Prioritise pensions first, then LISAs, and ISAs come last.
SIPPs vs ISAs: £47,417 Comfortable annual retirement income
SIPP contributions are made at the basic income tax rate in this scenario. The 25% tax-free cash cap is reached after 23 years of retirement.
Ranking | PA intact | Retire on State Pension | 40-yr retirement |
1. | LISA / Salary sacrifice | LISA | LISA |
2. | – | Salary sacrifice | Salary sacrifice |
3. | SIPP | SIPP | SIPP |
4. | ISA | ISA | ISA |
LISAs have reeled in salary sacrifice SIPPs across the board at the Comfortable income level.
Meanwhile, SIPPs only just beat ISAs across a 40-year retirement because the tax-free cash spigot splutters dry after 24 years.
However, it’s possible to avoid this fate by pulling out your 25% tax-free cash as a lump sum (PCLS) before the ceiling is reached.
Ideally, you’d get it all under ISA cover as quickly as possible. Once in an ISA your money can continue to grow tax-free without limit. (That is, as if the tax-free cash cap had not been introduced.)
How doable is that?
Sheltering your tax-free lump sum
Let’s say you retire in late March and deliberately leave that year’s ISA allowance free until then. That’s £20,000 under your tax shield straightaway.
The tax year clock ticks on to April 6. Now you’ve got another £20,000 worth of ISA to fill with newly-minted 25% tax-free cash.
Perhaps you also have some emergency cash standing by, an offset mortgage facility, or other cash savings?
With a bit of planning, you can use these resources to expand your flexible ISA’s elastic band in the years before your retirement date.
Check out the ‘Flexible ISA hack to build your tax-free ISA allowance’ section in our ISA allowance post. (Hat tip to Finumus who came up with the idea.)
Double your ISA allowance numbers if you have a trustworthy significant other.
You’ll be able to stash a bit more tax-free in General Investment Accounts, too. However, the much-shrunk dividend tax and Capital Gains Tax allowances mean that only a smidge of your subsequent returns will escape HMRC’s tractor beam.
All the same, you’re better off being taxed at dividend and capital gains rates than income tax rates. Hence you should withdraw any 25% tax-free cash as soon you can, once you look like you’ll hit the cap. It’s better out than in.
If the 25% tax-free cash is eliminated
Ranking | PA intact | Retire on State Pension | 40-yr retirement |
1. | LISA | LISA | LISA |
2. | Salary sacrifice | Salary sacrifice | Salary sacrifice |
3. | SIPP | ISA | ISA |
4. | ISA | SIPP | SIPP |
Notice that a SIPP actually performs worse than an ISA in the main two scenarios. That’s because a ‘Comfortable’ income earner ends up being partially taxed at the higher-rate, once you add on their State Pension.
This scenario could unfold for a basic-rate worker who saved into their SIPP from a young age, experienced outstanding investment performance, or suffered elevated tax rates in retirement.
Aside from that, frozen tax thresholds and the pernicious effects of fiscal drag make it increasingly likely that retirees will be dragged into the 40% band.
The SIPP vs ISA rankings for higher-rate taxpayer contributions differ slightly from the Minimum income level.
The ranking is: Salary sacrifice SIPP, non-salary sacrifice SIPP, LISA, then finally ISA.
Except… that LISAs and non-salary sacrifice SIPPs are tied if you retire at the State Pension age.
LISAs vs SIPPs: tie-breaker situation
There are quite a few scenarios that end in a draw between LISAs and pensions. Let’s head into the tie-breaker:
Priority | LISA | SIPP |
Access before age 60 | No | Yes |
Can help to buy a house | Yes | No |
Inheritance tax benefit | Spouse | Spouse6 |
Means-testing / bankruptcy advantage | No | Yes |
Tax-strategy diversification | Use | both |
I don’t think the few years’ gap in account accessibility is an issue. You can always drawdown harder on pensions until age 60.
Interestingly, the government seems to have cooled its jets on advancing the normal minimum retirement age in lockstep with the State Pension age.
Accessibility aside, the LISA’s low allowance, restrictions on contributions beyond age 50, plus the principle of tax-strategy diversification all suggest maxing out the LISA if/while you can.
That goes double if your financial position means that salary sacrifice actually makes you worse off. Hit that link for the gory details.
Pensioned off
There have probably been retirements that lasted less time than it took to write this post. Alas recent developments have not made the SIPP vs ISA question any easier to answer, I’m sorry to say.
But I hope this guide helps you think through the options. Assuming you haven’t lost the will to live in the meantime.
Do I need to plug taking your employer pension contributions one more time? Probably not…
Take it steady,
The Accumulator
P.S. Here’s more on how much should you should put in a pension and how much you need to retire.
P.P.S. We’ve updated this post as noted to reflect the latest output of our fearsome spreadsheets given today’s realities. Many comments below will refer to the earlier iteration of the post, so please have a care when perusing.