UK retirement drawdown strategy: SIPP, ISA and GIA sequencing

1. The three account types and how they are taxed

UK savers approaching retirement typically hold wealth across a SIPP, an ISA and a general investment account. Each is taxed differently on growth and on withdrawal, and it is that difference in timing that sequencing exploits.

SIPPs are funded from pre-tax money: you get relief on contributions and the fund grows free of income and capital gains tax, but withdrawals above the tax-free element are taxed as income. That deferred tax bill is the central challenge of pension drawdown. ISAs work the other way — contributions come from taxed income, but growth is sheltered and every withdrawal is tax-free with no reporting. The £20,000 annual allowance caps what goes in; there is no cap on what comes out. GIAs carry no wrapper: gains are taxed on disposal, dividends above the allowance are taxed, and interest is taxed as savings income.

Nothing in UK law dictates the order you draw in. That flexibility is valuable only if you use it deliberately — and most retirees don’t, defaulting to the largest or most accessible pot. The question tax-efficient sequencing answers is: given your balances, your income needs and the rules, what combination of withdrawals each year minimises cumulative lifetime tax? Minimising tax in year one and minimising it over thirty years can point in opposite directions.

The optimal sequence also isn’t fixed. It depends on returns, longevity, inflation, tax-law change and life events. Monte Carlo simulation addresses this by running your strategy across thousands of simulated market paths, so you can see not just whether it works in the expected case but how robust it is under stress. EnoughDay stress-tests plans against historical UK sequences as well as simulated ones.

2. SIPP withdrawal strategy

The end of the Lifetime Allowance

The Lifetime Allowance charge was removed in April 2023 and the allowance abolished from 6 April 2024. In its place sits the Lump Sum Allowance of £268,275 — the cap on total tax-free cash across all your registered schemes. For most savers with standard pots this doesn’t change the core strategy; for very large SIPPs, the removal of the LTA charge changed the calculus around deferral.

Tax-free cash: take it early or defer?

Up to 25% of a pot can be taken as a Pension Commencement Lump Sum, tax-free, subject to the £268,275 cap; the remaining 75% is taxed as income when withdrawn. Taking cash early gives you a sum to place in an ISA (within the allowance) or a GIA; deferring lets the untouched pot grow, though 75% of that growth is eventually taxed as income. There is no universal answer — it turns on your retirement income, tax band, return assumptions and longevity, which is exactly the kind of trade-off a model that tests both paths handles better than a rule of thumb.

Income tax on pension withdrawals (2026/27)

Pension income above your tax-free cash sits alongside your other income. For the rest of the UK in 2026/27:

• Personal allowance: £12,570 — income below this is tax-free
• Basic rate (20%): £12,571 to £50,270
• Higher rate (40%): £50,271 to £125,140
• Additional rate (45%): above £125,140

Stay below £50,270 and the taxable portion is taxed at 20%; cross it and the marginal rate doubles. That gap drives how much pension it is efficient to draw each year.

Preserving the personal allowance

The £12,570 personal allowance is the most valuable tax-free band a retiree has. In early retirement — before the State Pension starts — many have little or no other taxable income, so drawing pension income up to the allowance each year uses the entitlement, reduces the pot’s future income-tax liability, and costs nothing. This “pension smoothing” spreads withdrawals across low-income years rather than leaving a larger bill for later, once the State Pension arrives and fills most of the allowance automatically.

The 60% band, and the interaction with the State Pension

Above £100,000 of adjusted net income the personal allowance tapers at 50p per £1, disappearing at £125,140 — an effective 60% marginal rate on income between the two. Pension withdrawals that stray into that range cost 60p of tax on every extra pound. Lower down, the High Income Child Benefit Charge bites between £60,000 and £80,000 for those still receiving Child Benefit.

The full new State Pension is £12,547.60 in 2026/27 — it consumes nearly all of the £12,570 personal allowance on its own. Once it starts, only about £22 a year of further pension income stays tax-free; the rest is taxed at 20% or more. That is why the years between pension-access age and State Pension age are so valuable: in that window you can draw against the full allowance before the State Pension fills it. Deferring the State Pension (which uplifts it by roughly 5.8% a year) rarely helps an early retiree already drawing pension income, but can suit someone who returns to work and wants to keep other income out of a higher band.

3. ISA withdrawal strategy

ISA withdrawals are completely tax-free — no income tax, no CGT, no dividend tax, no reporting. Because they don’t touch your tax band, the personal-allowance taper, the State Pension interaction or means-tested entitlements, the ISA is the pot most worth preserving. In a well-ordered drawdown it tends to come last, after SIPP and GIA, since its tax-free status compounds the longer it runs. That is a tendency, not an absolute rule: drawing ISA earlier makes sense to cover a large one-off cost cleanly, to rebalance without a taxable disposal, or to bridge income without pushing into a higher band.

Lifetime ISA and asset location

A Lifetime ISA (opened between 18 and 39) takes up to £4,000 a year within the overall allowance and adds a 25% government bonus. Withdrawing before age 60 for anything other than a first home incurs a 25% charge on the whole withdrawal — which can leave you with less than you put in — so a LISA is effectively illiquid before 60 and sits late in the early-retirement sequence. From 60 it behaves like any Stocks & Shares ISA. Separately, because ISAs shelter growth, they are most valuable holding your highest-growth assets — holding cash or bonds in an ISA while high-growth equities sit taxable in a GIA is a common and costly mistake.

4. GIA (taxable account) strategy

When you sell an asset in a GIA you pay CGT on the gain. In 2026/27 the annual exempt amount is £3,000; above it, investment gains are taxed at 18% within the basic-rate band and 24% above the higher-rate threshold (residential property uses the same 18%/24% rates). Your income level sets which applies: a year with low pension withdrawals leaves more room for GIA disposals at 18% rather than 24%.

Dividends are taxed separately. The 2026/27 dividend allowance is £500; above it, dividends are taxed at 10.75% for basic-rate taxpayers, 35.75% at higher rate and 39.35% at additional rate (the basic and higher rates rose by two percentage points from April 2026 under Finance Act 2026). Dividends stack on top of other income, so a high-yield portfolio in a GIA can quietly push you into a higher band — an argument for holding high-dividend assets inside an ISA or SIPP. Interest is taxed as savings income above the Personal Savings Allowance (£1,000 basic rate, £500 higher rate, £0 additional).

Bed-and-ISA, and where the GIA sits

HMRC’s 30-day “bed and breakfast” rule stops you selling and instantly repurchasing the same asset to reset a gain. Within it, you can still crystallise gains within the annual exemption and buy back after 30 days, or run a bed-and-ISA — sell in the GIA and repurchase inside the ISA using that year’s allowance, sheltering future growth. Losses can be crystallised and carried forward too. In the drawdown sequence the GIA is usually tactical rather than the anchor: it fills the gap between the personal-allowance-limited pension draw and an ISA you’d rather leave to compound. Transfers between spouses are CGT-neutral, which lets a couple move GIA assets to the lower-rate partner before disposal.

5. Sequencing in practice

Consider Alex, 55, newly retired with £500,000 in a SIPP, £300,000 in a Stocks & Shares ISA, £200,000 in a GIA, no State Pension yet, £30,000 of annual spending and no other income.

Year 1. Alex draws £12,570 from the SIPP against the personal allowance — tax £0. The remaining £17,430 comes from the GIA. With, say, a £5,000 gain on those disposals, £3,000 is covered by the annual exemption and the remaining £2,000 is taxed at 18% (Alex’s income is far below £50,270): £360 of CGT. Total tax in year one: £360 on £30,000 of spending — about 1.2%. The ISA is untouched and keeps compounding. The rough logic that follows:

1. SIPP first, up to the £12,570 personal allowance — tax-free income.
2. GIA next, using gains within the £3,000 CGT exemption — little or no tax.
3. GIA disposals into the basic-rate band — 18% CGT where gains exceed the exemption.
4. ISA last — tax-free, preserved for later years when other allowances are spent.

The order shifts once the State Pension fills the allowance, once the GIA is largely spent, or once the ISA has grown enough to be the efficient source. It also has to flex to events. If markets fall hard in year three, a rigid plan might keep selling GIA assets at a loss; instead, crystallising those losses to carry forward, and bridging living costs with a tax-free ISA withdrawal, avoids locking in the loss and adds nothing to taxable income. And if Alex realises a large gain in a later year — say a £100,000 gain on a property that isn’t covered by Private Residence Relief — keeping other income near zero that year lets the whole gain sit in the basic-rate band: 18% on £97,000 after the exemption is £17,460, far less than if a full year of pension income were stacked on top.

6. Common pitfalls and edge cases

Wasting the ISA wrapper. Holding cash or bonds in an ISA while equities sit taxable in a GIA shelters the wrong assets. The fix — moving growth assets into the ISA gradually via bed-and-ISA — is manageable over several years using the annual exemption.

Ignoring a spouse’s allowances. Every adult holds their own personal allowance (£12,570), CGT exemption (£3,000), dividend allowance (£500), savings allowance (up to £1,000) and ISA allowance (£20,000). Drawing all income through one partner leaves the other’s entitlements — and a second £3,000 CGT exemption — unused.

Treating sequencing as a one-off. A plan drawn up at 55 needs revisiting after an inheritance, a property sale, a return to work, or a change in a spouse’s income — ideally once a year and after any major event.

Scottish thresholds. Scottish income tax has six bands in 2026/27 — starter 19%, basic 20%, intermediate 21%, higher 42%, advanced 45% and top 48% — with the higher rate starting at £43,662 against £50,270 for the rest of the UK. The principles here are unchanged; the numbers differ, and the efficient pension-drawdown window is narrower.

Inheritance and the April 2027 change. Historically, unused pension funds have sat outside the estate for inheritance tax, which made pensions the most IHT-efficient asset to pass on and argued for spending ISA and GIA first where a legacy mattered. That changes: from 6 April 2027 unused pension funds are brought inside the estate for IHT. Where death is after age 75 the beneficiary can also pay income tax on what they draw, on top of any IHT — a double layer the case for hoarding a pension unspent no longer survives. The pensions-into-IHT 2027 calculator estimates the effect for a given pot and estate.

7. Why a spreadsheet alone isn’t enough

A good spreadsheet models one path clearly, and many numerate savers build exactly that. The limit is that it handles one scenario at a time — a best, base and worst case is still just three paths through a thirty-year retirement, and sequence-of-returns risk (a crash early on) is hard to stress-test by hand. Monte Carlo simulation runs thousands of randomised paths consistent with your return, volatility and inflation assumptions and reports a distribution: what share of futures still leave money at 90, and how the plan fares in the worst tenth of outcomes.

EnoughDay models your SIPP, ISA and GIA against the full 2026/27 tax code — income tax including Scottish bands, CGT, dividend and savings taxation, the State Pension and the threshold interactions — and reports the withdrawal order for each year, the cumulative tax under that order versus the alternatives, and the date your portfolio can sustain your target income across the simulated distribution. Every year’s figure expands to show what was drawn from which account and what tax arose, so you can check it against your own spreadsheet rather than take a headline on trust.

Worked examples are illustrations on 2026/27 rules, and tax law changes regularly, so verify current thresholds with HMRC. EnoughDay provides information and planning tools, not financial advice. Projections are illustrations, not guarantees. For personal recommendations, consider a regulated financial adviser.