FIRE glossary
Tax Drag on Withdrawals
The gap between the gross amount you must withdraw from a taxable account and the net amount you actually get to spend, once income tax on the drawdown is paid.
How Ember calculates it
Ember doesn't tax a lump sum once and stop there — it solves for the gross withdrawal that nets your target spend after tax, using a fixed-point iteration that converges to the nearest penny in well under a dozen passes. The starting point is your investable portfolio's taxableShare: a value-weighted fraction of each pound drawn that counts as taxable income. You tag each holding — a general investment account or a SIPP typically taxable, a stocks & shares ISA or similar tax-free wrapper not — and Ember weights across your whole portfolio by value to get one blended figure. Non-investable assets — your home, a car — are excluded entirely; they were never part of the drawdown pot to begin with.
It's never drag in isolation
Ember also runs an items-aware version of the same solve that stacks your withdrawal on top of any pension or rental income landing in the same tax year, before working out the gross figure. That matters because income tax bands are progressive: a draw sitting on top of a decent pension income lands in a higher marginal band than the identical draw with no other income that year, so the same withdrawal can carry more or less drag depending on what else you're receiving alongside it.
Where drag comes from — and where it doesn't
Tax drag is entirely a function of taxableShare. A pot built entirely from tax-free wrappers has a taxableShare of zero and no drag at all — the gross figure equals the net figure exactly, and the solve exits immediately. A pot weighted toward a fully taxable account has the opposite: more of each pound drawn passes through income tax before it reaches you, so hitting the same net spend means pulling out noticeably more gross.
Across borders
Every jurisdiction Ember covers has its own income tax bands, so the same taxableShare and the same net spend target can gross up to a very different number depending on where you're tax resident when you draw it — moving to a country with no income tax collapses the gross-up to zero, moving to a steeply progressive one can inflate it substantially. A relocation partway through retirement changes which country's bracket table the solve uses from that point on, which is one of the concrete ways crossing a border changes your required pot, not just your cost of living — see geoarbitrage for the other half of that same move.
Common questions
Does tax drag affect my FIRE number?
Yes, directly. Ember's required-pot calculation grosses your spend target up for tax drag before dividing by the withdrawal rate, so a portfolio weighted toward taxable accounts needs a larger pot for the same net lifestyle than an identical portfolio held in tax-advantaged wrappers. See the safe-withdrawal-rate term.
Can I reduce tax drag without changing my spending?
In the model, only by changing what taxableShare looks like for your portfolio — holding more of the drawdown pot in tax-advantaged wrappers, or seeing how the draw interacts with other income landing in the same tax year. Ember doesn't recommend a specific account structure; it shows the trace behind the gross-up so you can see how sensitive your required pot is to the mix you enter.
Is tax drag a one-off cost or does it recur every year?
It recurs every year you draw from a taxable account in retirement — it isn't a one-off hit, which is why Ember bakes it into the required-pot maths rather than treating it as an afterthought or a separate adjustment.
Related terms
See tax drag on withdrawals in your numbers
The free calculator gives a rough estimate; the full planner models your actual accounts, pensions, residency moves and taxes — with the maths behind every figure shown.