Understanding marginal tax rates above £100,000
Marginal tax rates describe the effect of earning an additional unit of income.
Above £100,000, the marginal impact can differ materially from headline tax rates.
Marginal vs headline rates
Headline rates show how income bands are taxed.
Marginal impact reflects:
allowance withdrawal
entitlement loss
threshold interactions
These factors can combine to produce outcomes that are not immediately visible.
Why marginal impact varies by circumstance
The marginal effect of additional income depends on:
how income is structured
which allowances apply
which entitlements are relevant
As a result, two individuals with similar incomes may experience different outcomes.
Why generic answers are unreliable
Because multiple thresholds may apply simultaneously, the marginal impact above £100,000 is highly circumstance-specific.
Understanding it requires looking at how rules interact in combination.
Further analysis
A personalised written analysis can show the marginal impact of additional income in your circumstances.
View the £100k Cliff Edge Report
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