As a high-income professional in the UK —perhaps you’re a doctor, lawyer, consultant, senior manager—and you also happen to be a US citizen; you’ve got to deal with tax rules from two countries. That often puts you in a tricky position where the UK wants you to save in one way and the US nudges you towards another. Taper Relief could be impacting you. Basically you have a large salary but only a small pension amount you can contribute each year.

When it comes to retirement savings, both countries offer generous tax-advantaged accounts. In the UK, you’ve got pensions. In the US, you’ve got IRAs (plus 401(k)s).

Here’s the problem. As a high earner in the UK, something called “taper relief” limits the amount you can put into your pension each year. But at the same high-income levels, US tax law prevents you from contributing to a Roth IRA. Frustrating, right? I mean, you want to save for retirement just like everyone else, but the system seems designed to make it difficult.

Why High Earners Hit a Wall with UK Pensions

OK, let’s start with pensions, because this is where many high earners first hit a roadblock. If you are a salaried employee in the UK, you can save into a pension and get tax relief on your contributions. Up to £60,000 per year, in fact.

That’s called your annual allowance, and for many people it’s one of the best ways to accumulate long-term wealth. Why? Well it’s pretty simple. If you pay £10 into your pension, the government gives you tax relief of up to £40%. In effect your money is getting a large markup.

But here’s the thing. Once your income passes a certain level, that annual allowance starts to reduce. It goes down as your income goes up. This is known as **taper relief.

UK pension taper relief was explicitly designed to restrict how much high earners can save in their pensions each year.

If your income is high enough, it can disappear all together. The annual allowance can eventually shrink to as little as £10,000.

The frustrating part is the limits aren’t based on your salary alone. They’re based on what’s known as your “threshold income” and “adjusted income”. There are various nuances that determine what counts towards each of those figures.

What happens in practice is lots of people don’t realise they’re affected by taper relief until it’s too late. They discover come January that they’ve breached their pension allowance for the previous tax year.

In short: as your income rises, you lose one of the best tax-efficient wrappers for your retirement savings.

So Where Else Can You Save?

If you can’t save into UK pensions any more (or at least not as much), where can you save? Well, as a UK taxpayer you could stick your money in an ISA or a standard investment account. If you rent property, you could put money into real estate.

You could do all of those things. But what about retirement accounts? Aren’t there any other places you can save?

That’s where your US citizenship comes in. As a US citizen, you have access to a bewildering array of retirement accounts. Contributions into many of these are tax deductible, and some even offer tax-free growth and withdrawals. The most well-known example is probably the Roth IRA.

What Makes a Roth IRA So Powerful?

A Roth IRA gets its power from how it is taxed. When you put money in, it comes from after-tax income. You won’t get an upfront tax break. But everything that grows in the account from there is yours to keep—tax-free.

Your investments grow without being taxed each year. And then, when you eventually retire and withdraw the money, you never pay tax on it again (as long as you follow the rules). Tax-free growth and withdrawals? That’s incredibly rare. It means the money you build inside a Roth IRA account essentially falls outside of the tax system when you retire. For high earners, this offers powerful flexibility. Once you retire you can pick and choose whether to take taxable income or Roth IRA withdrawals. You optimise for tax efficiency each year.

The Problem: High Earners Are Blocked

Roth IRAs don’t let high earners contribute. Like UK pensions, your income starts to exceed thresholds where you can no longer contribute directly to a Roth. If you can’t contribute directly, does that mean the door is closed? Nope. As it turns out, there’s a workaround. This is where things get interesting.

The Backdoor Roth IRA: A Legal Workaround

Even if you’re a high-income earner, you can still contribute to a Roth IRA. It just takes a few extra steps. This is known as a Backdoor Roth IRA conversion. Sound complex? It’s not. Let’s break it down.

The core strategy involves funding a Traditional IRA initially. Then, immediately convert (or move) that money into a Roth IRA. If you earn too much income to contribute to a Roth directly, you can’t do the first step. But there are no income limits on contributions to Traditional IRAs. The only catch is that if you’re a high-income earner, you probably won’t get a tax deduction for that contribution. Basically, you pay taxes on the money up front. So when you move it to the Roth, there isn’t anything left for the IRS to tax—you already paid!

Where It Gets Complicated: The Pro Rata Rule

The not-simple part of this strategy is called the pro rata rule. Here’s the basic idea: when you convert money from a Traditional IRA to a Roth IRA, the IRS doesn’t care where that money came from. It treats ALL of your IRA money as one pool. This includes:

Traditional IRAs
SEP IRAs
SIMPLE IRAs

If you have money in any of these accounts that was not contributed with after-tax dollars, then the pro rata rule comes into play. Basically, it says that anytime you convert money from a Traditional IRA to a Roth, you must include SOME pre-tax dollars in that conversion. You can’t just say, “Please tax me on this amount I converted, but nothing else.”

A Simple Example

Imagine you have two types of money in IRAs:

USD7,000 (or dollar equivalent) of after-tax contributions that you just made
USD93,000 of pre-tax money sitting in another IRA

From your perspective, you might think: “I’ll just convert the 7,000 I just added, and since I already paid tax on it, there should be no tax due.”

But the IRS sees things differently. It combines everything and says: you have 100,000 total, and only 7% of it is after-tax.

So if you convert £7,000, only 7% of that conversion is treated as tax-free. The remaining 93% is treated as taxable income.

That can create an unexpected tax bill, which defeats much of the benefit of the strategy.

The Key Insight: Keeping Your IRA “Clean”

To make the Backdoor Roth strategy work efficiently, many high earners aim to keep their IRA balances “clean.” What this means in practice is having little or no pre-tax money sitting in Traditional, SEP, or SIMPLE IRAs.

One common way to achieve this is by moving existing IRA funds into an employer-sponsored retirement plan, such as a 401(k), if that option is available. These plans are not included in the pro rata calculation, which allows you to separate your pre-tax and after-tax money more effectively.

Once your IRAs contain only after-tax contributions, the Backdoor Roth process becomes much cleaner and more predictable from a tax perspective.

How UK Pensions Fit Into All This

If you are based in the UK, you might be wondering whether your UK pension affects any of this.

In general, UK pensions are treated separately from US IRAs. They are typically covered under the US–UK tax treaty and are not included in the pro rata calculation.

This is helpful, because it means your UK pension—no matter how large—does not interfere with your ability to use the Backdoor Roth strategy.

However, this does not mean they are ignored entirely. As a US citizen, you still need to report foreign financial accounts, and there are specific rules around how pensions are taxed and disclosed. So while they do not affect the pro rata rule, they are still part of your overall planning picture.

Bringing It All Together

For a high-earning dual US/UK professional, the most effective approach is usually not about choosing one system over the other, but about using both intelligently.

Even if taper relief limits how much you can contribute to your UK pension, it often still makes sense to take advantage of employer contributions and any available tax relief.

At the same time, the Backdoor Roth IRA gives you a way to continue building tax-efficient retirement savings on the US side, even when your income is too high for standard contributions.

The real value comes from combining these strategies. You end up with different “buckets” of money:

UK pension assets, which are tax-deferred
Roth IRA assets, which can be tax-free in retirement
Possibly other investments, which may be taxable

Having multiple types of accounts gives you flexibility later in life. You can decide where to draw income from depending on tax rates, currency considerations, and your personal circumstances at the time.

Effective long term strategy for Pension asset growth where you are capped

The rules around taper relief and the Backdoor Roth IRA can seem technical, and in some cases they are. But at their core, they are about understanding how different parts of the system interact.

If you take the time to structure things properly—especially being mindful of the pro rata rule—you can continue to grow your retirement assets in a tax-efficient way, even at very high income levels. And for someone navigating both the UK and US systems, that kind of flexibility is not just helpful—it’s essential.