Tax relief arrives in two structurally different forms, and they are frequently discussed as though they were the same thing. The difference determines who benefits and by how much.
The two operate at different points
A deduction is subtracted from income before the tax calculation runs, so it reduces the amount of income exposed to tax.
A credit is subtracted from the tax figure after that calculation, so it reduces the bill directly rather than the base it was computed from.
The sequence is what matters. Anything applied before the rates are applied is worth the rate; anything applied afterwards is worth its face amount.
Deductions are worth more to higher earners
Because a deduction removes income from the top of the taxable amount, its value equals the deduction multiplied by the taxpayer's marginal rate.
The same deduction is therefore worth substantially more to someone in a high band than to someone in a low one, and worth nothing to someone with no taxable income.
This is not an oversight but a mechanical consequence, and it is why proposals to convert deductions into credits recur in policy debate.
Credits are flat unless designed otherwise
A credit reduces tax by its stated amount regardless of the taxpayer's rate, which makes its value identical across income levels within the eligible range.
Many credits are then phased out above an income threshold, which reintroduces variation but through an explicit policy choice rather than through the arithmetic.
That explicitness is the point. A credit's distribution can be designed, while a deduction's distribution follows automatically from the rate schedule.
Phase-outs do carry a hidden cost, because withdrawing a credit as income rises adds to the effective marginal rate over that range without appearing in the published bands.
Refundability changes the picture again
A non-refundable credit can only reduce tax to zero. Any excess is lost, so a taxpayer with little liability captures only part of the intended benefit.
A refundable credit pays out the excess, which means it can deliver value to someone who owes no tax at all.
Refundability is therefore the feature that determines whether a credit reaches lower-income households, and it is often the most contested element of any such measure.
Comparing headline amounts is misleading
A large deduction and a small credit can be worth the same amount, and which is better depends entirely on the individual's rate and liability.
Descriptions that quote face values without stating the mechanism make relief sound larger or smaller than it is.
Which reliefs exist, how they interact and whether they are refundable differ by jurisdiction and change frequently, so any specific comparison needs checking against current local rules.