Pension vs ISA: Where Should Your Money Go First

I get asked this more than almost anything else. Should I put my money into a pension or an ISA? And the answer is annoyingly unsatisfying: it depends on when you need the money.

When I was building towards early retirement, I had to think about this properly. I was leaving work at 40 but could not touch my pension until 57. That is a 17-year gap. If I had put everything into my pension, I would have been financially independent on paper but completely skint in practice. The money would have been there, locked behind a glass wall I could not break for nearly two decades.

So I did both. And the order I filled them mattered enormously.

What a pension gives you

A pension is the most tax-efficient savings vehicle in the UK. Full stop. The tax advantages are genuinely hard to beat:

Tax relief on contributions. A basic rate taxpayer gets 20% tax relief. Put in £800, the government tops it up to £1,000. Higher rate taxpayers can claim back a further 20% through self-assessment, meaning £1,000 in the pension costs you just £600.
Employer matching. If your employer matches contributions, that is an immediate 100% return on the matched amount. There is no investment in the world that guarantees that.
Tax-free growth. Everything inside your pension grows free of income tax and capital gains tax.
25% tax-free lump sum. When you access your pension, the first 25% comes out completely tax-free.
Salary sacrifice benefits. If your employer offers salary sacrifice, you also save on National Insurance. For a higher rate taxpayer, the effective cost of a £1,000 pension contribution can be as low as £580.

Those are significant advantages. But pensions come with strings attached.

The downsides:

Locked until 57. You cannot access your pension until age 55 (rising to 57 in 2028). If you need the money before then, it does not exist to you.
Complex rules. Annual allowance (£60,000), money purchase annual allowance if you have already started drawing, lifetime allowance replacement rules. It is a minefield.
Tax on withdrawal. Everything beyond your 25% tax-free lump sum is taxed as income. If you withdraw too much in one year, you could push yourself into a higher tax bracket.
Inheritance tax changes from 2027. From April 2027, pension pots will be included in your estate for inheritance tax purposes. This is a major shift. Previously, pensions sat outside your estate entirely.

What an ISA gives you

An ISA is simpler. You put money in (up to £20,000 per tax year), and everything inside it, the growth, the dividends, the interest, is completely tax-free. When you take money out, there is no tax to pay. None.

The advantages:

Flexible access. You can withdraw from an ISA whenever you want, at any age, for any reason. No penalties. No tax. No waiting until 57.
No tax on withdrawals. Unlike a pension, you pay zero tax when you take money out of an ISA. This matters if you are a higher rate taxpayer in retirement.
Simple rules. The main rule is the £20,000 annual limit. Beyond that, ISAs are straightforward.
No inheritance tax complications. ISAs form part of your estate, but there are no recent rule changes complicating things.

The downsides:

No tax relief on contributions. You contribute from post-tax income. There is no government top-up. A £1,000 ISA contribution costs you £1,000.
£20,000 annual limit. The pension annual allowance is £60,000. The ISA allowance is £20,000. If you have significant sums to shelter, pensions offer more room.
No employer matching. Nobody matches your ISA contributions. That free money only exists with pensions.

The decision framework

Here is how I think about it, and it is the same framework I would give to anyone asking.

Step 1: Get the employer match

Before anything else, contribute enough to your workplace pension to get the full employer match. If your employer matches up to 5%, contribute 5%. This is a guaranteed 100% return. There is no scenario where skipping this makes sense, not even if you have debt (with the possible exception of very high-interest debt above 15% or so).

Step 2: Fill the ISA for pre-57 access

If you are planning to retire before 57, or if you simply want money you can access at any time, your stocks and shares ISA comes next. You can put in up to £20,000 a year and everything grows tax-free.

This was critical for me. My ISA portfolio is what funds my life from 40 to 57. Without it, early retirement would not have been possible. Even if you are not planning to retire early, having accessible money outside your pension gives you options. Redundancy, career changes, opportunities that require capital. Life does not always wait until you are 57.

Step 3: Fill the pension for tax relief

Once your ISA is maxed, go back to the pension. The tax relief is too good to ignore, especially if you are a higher rate taxpayer. Every £1,000 you contribute effectively costs you £600 (or £580 via salary sacrifice). That is a level of tax efficiency an ISA simply cannot match.

If you cannot max both, prioritise the ISA up to the amount you think you will need before 57, and put the rest into your pension.

Step 4: The exception for very high earners

If you are a higher or additional rate taxpayer and you do not need money before 57, the pension arguably comes before the ISA (after employer matching). The 40% or 45% tax relief is so valuable that the locked access becomes worth the trade-off. You are getting back nearly half of every pound you contribute. That is hard to replicate elsewhere.

How I structured it for early retirement

My approach was built around one reality: I needed money from age 40 to 57 (ISA territory) and then from 57 onwards (pension territory).

During my earning years, I:

Maxed my employer pension match first
Filled my stocks and shares ISA to £20,000 every year
Put additional money into my SIPP up to the annual allowance
Anything beyond that went into a general investment account

The ISA became my bridge fund. The pension became my long-term fund. The ISA gets me from 40 to 57. The pension, combined with the state pension later, covers 57 onwards.

If you are not retiring early, the split is simpler. Get the employer match, fill the ISA, then fill the pension. That order gives you both tax efficiency and flexibility.

The one mistake I see constantly

People max their pension and ignore their ISA. They get to 50 and realise they have £400,000 locked away and £12,000 in a savings account. They are pension-rich and cash-poor.

A pension is brilliant for retirement. But life happens before retirement too. Having accessible, tax-free money in an ISA gives you options that a pension cannot. Redundancy cover. A house deposit. A business opportunity. The ability to retire before 57.

Fill both if you can. But if you have to choose, ask yourself one question: when do I need this money? The answer tells you exactly where it should go.

Pension vs ISA: Where Should Your Money Go First?