How to Learn Tax Incidence Quickly and Correctly

How do you learn Tax Incidence quickly and correctly when a government says a tax must be paid by a business? Start by separating who sends the money to the tax authority from who actually bears the economic burden. These need not be the same person. This eduKateSG Economics Quick Notes lesson uses an imaginary market to explain prices paid by buyers, prices received by sellers, the tax wedge, demand and supply elasticity, and the difference between tax revenue and lost gains from trade. The lesson is about a simplified per-unit tax, not a statement about Singapore’s current tax rules.

Identify: the price before the tax.
Compare: the new buyer price with the net price sellers receive.
Find: the per-unit tax wedge between those two prices.
Split: calculate the buyer and seller portions of that wedge.
Explain: the less price-responsive side of a competitive market generally bears more of a tax’s economic burden.

Teaching step 1 — begin with a market price. Imagine a fictional school-fair market where an item originally sells for S$10. A government then introduces a S$2 per-unit tax on transactions in this good. After buyers and sellers adjust, suppose buyers pay S$11.20 per item, while sellers receive S$9.20 per item net of tax. The gap between the two prices is S$11.20 − S$9.20 = S$2, exactly the tax. The amounts are invented for teaching. Notice the important difference: buyers pay one price; sellers keep another.

Teaching step 2 — calculate who bears how much. Before the tax, buyers paid S$10; now they pay S$11.20. Their extra price burden on each remaining purchase is S$1.20, or 60% of the S$2 wedge. Sellers previously received S$10; now they keep S$9.20. Their reduction is S$0.80, or 40% of the wedge. The shares add to 100%. Even if a law tells sellers to remit all S$2 to the authority, it does not follow that sellers carry all S$2 economically. Their ability to adjust prices matters.

Teaching step 3 — connect tax incidence with elasticity. Suppose buyers have few good alternatives and change their purchases very little when the price rises, while sellers can readily switch resources to other products. In a standard competitive-market model, buyers tend to bear more of the per-unit tax because demand is less elastic than supply. If buyers can switch easily but sellers cannot reduce supply, sellers tend to bear more. The rule to remember is not ‘the tax always falls on customers’ or ‘the business pays’; it is that the more inelastic side generally bears the larger share, given the model’s assumptions.

The three prices to keep separate

A tax-incidence diagram has three central price labels. P0 is the market price before the tax. Pc is what consumers pay after the tax. Pp is what producers receive after the tax, net of the duty. In the teaching example, P0 = S$10, Pc = S$11.20 and Pp = S$9.20.

The per-unit tax is Pc − Pp = S$2. The consumer’s per-unit price increase is Pc − P0 = S$1.20. The producer’s per-unit decrease is P0 − Pp = S$0.80. Add the last two figures and you should recover the S$2 tax wedge.

These comparisons describe price incidence on remaining transactions. They do not exhaust every welfare effect: buyers and sellers may lose additional opportunities because fewer trades take place.

Before-tax market price: P0 = S$10.
After-tax buyer price: Pc = S$11.20.
After-tax seller receipt: Pp = S$9.20.
Tax wedge: Pc − Pp = S$2.
Buyers’ share: (Pc − P0) ÷ S$2 = 60%.
Sellers’ share: (P0 − Pp) ÷ S$2 = 40%.

Statutory incidence versus economic incidence

Statutory incidence concerns which party the law requires to pay or remit a tax. Economic incidence concerns who ultimately bears a real cost as prices, wages, rents or returns adjust. These concepts are often different.

Imagine a seller receives S$11.20 from a customer, passes S$2 to the authority and retains S$9.20. The seller remits the whole statutory amount in this example. But the seller is receiving S$0.80 less than before while the buyer pays S$1.20 more than before. The economic burden is divided.

Equally, requiring the buyer to remit a tax does not necessarily guarantee the buyer ultimately bears it all. With the same competitive demand and supply assumptions, the resulting allocation of the tax burden can be similar even when the legal remitter changes. Compliance costs and market institutions may complicate the real-world outcome.

How elasticity determines who bears more

Think of elasticity as the ability or willingness to change behaviour when a price changes. If demand is relatively inelastic, buyers are less likely to stop purchasing after a price increase. Sellers can pass a larger part of the tax into the buyer price, other things equal.

If supply is relatively inelastic, sellers have fewer alternatives to producing or supplying the good. They may accept a bigger drop in what they receive rather than lose many transactions. The less elastic side is typically less able to avoid the market’s adjustment.

Do not confuse inelastic with an absolute inability to change. The comparison is relative. Demand may be somewhat responsive but still less responsive than supply; the buyers may then bear most of the burden without bearing all of it.

Demand less elastic than supply: buyers tend to bear more.
Supply less elastic than demand: producers tend to bear more.
Both respond: the burden can be shared.
Time matters: customers and producers may have more options in the long run than immediately after a tax.
Other markets matter: assumptions about competition, substitutes and input supply affect the result.

Calculate the government’s revenue from a per-unit tax

Suppose the fictional market sold 1,000 units before the tax and 800 units after the tax. If the tax is S$2 on every taxed unit and all are legally collected, government revenue is S$2 × 800 = S$1,600.

Using 1,000 units would incorrectly calculate S$2,000 because the tax changed the traded quantity in this example. Use the actual taxed quantity after the policy, not the original quantity, when calculating revenue.

Government revenue is not the same as the total burden borne by buyers and sellers measured in welfare terms. Some trades may no longer occur; changes in consumer surplus and producer surplus may exceed collected tax revenue.

Why a per-unit tax may reduce the quantity traded

In a competitive supply-and-demand diagram, the tax creates a wedge between what buyers pay and what sellers receive. A higher price to buyers discourages some purchases, while a lower receipt to producers discourages some production. The traded quantity may fall from the old equilibrium.

Some transactions that would have benefited both buyers and sellers at the original price no longer occur after the tax. Under a simple model without externalities or pre-existing distortions, this can create a deadweight loss: a reduction in combined surplus not collected as tax revenue.

Do not claim every tax is necessarily socially harmful. Taxes can address negative externalities, such as some pollution, and the resulting behaviour change may improve social welfare. The basic deadweight-loss diagram isolates a particular market model; an actual policy assessment must consider the purpose and broader effects.

Optional graph extension: where the triangle comes from

For an introductory straight-line demand and supply model with no existing market distortion, suppose quantity falls from 1,000 units to 800 units and the tax wedge is S$2 per unit. The typical deadweight-loss triangle has a height of S$2 and a width equal to the 200 lost transactions.

Using the area-of-a-triangle formula, deadweight loss is ½ × 200 × S$2 = S$200 in this special illustrative model. Its exact area depends on the shapes of the supply and demand curves and the appropriate welfare model; do not apply the triangle shortcut blindly to unrelated real-world data.

Check your axes: vertical is the good’s price and horizontal is quantity. The wedge is the vertical gap between buyer and seller prices. The lost quantity lies along the horizontal axis. Tax revenue is the rectangular area represented by tax per unit times quantity still traded, not the triangle.

A second example: sellers carry most of the burden

Imagine the original price remains S$10 and the per-unit tax is S$2, but the new buyer price is S$10.50 while the seller receives S$8.50. The price gap is still S$2. Buyers pay S$0.50 more per unit, or 25% of the wedge, while producers receive S$1.50 less, or 75%.

This could be consistent with a market in which demand is relatively elastic and supply relatively inelastic. Customers can switch to alternatives while sellers find it harder to reduce or redirect production. It illustrates why the identity of the statutory remitter is not enough to predict economic incidence.

You can now compare two markets with exactly the same S$2 duty but different economic burdens. Tax rate alone does not tell you who bears the costs.

Four mistakes to repair

Assuming the legally named taxpayer bears the full economic cost: compare actual prices paid and received.
Comparing Pc only with Pp: the wedge shows tax size, but incidence shares require the original price P0.
Using original quantity for tax revenue: apply tax per unit to the new taxable quantity.
Reversing elasticity: the more inelastic side tends to bear the greater share in the basic competitive model.
Treating government revenue as proof of welfare gain or loss: consider forgone trades, externalities and policy objectives.

Correction note: ‘I said sellers paid the whole S$2 because they remit the tax. Correction: the price increased S$1.20 for buyers and fell S$0.80 for sellers, so the economic burden was shared.’

A ten-minute tax-incidence learning routine

Minutes 1–2: write P0, Pc and Pp on one line.
Minutes 3–4: calculate the S$2 wedge and its S$1.20/S$0.80 division.
Minutes 5–6: convert those figures into 60% and 40% shares.
Minutes 7–8: explain how elasticities alter the split.
Minutes 9–10: calculate revenue with the new quantity and check a changed case.

When the arithmetic and economic meaning agree, the concept becomes easier to remember. If a graph confuses you, begin with the three prices before drawing the curves.

Quick Economics practice: answer before checking

1. Before tax an item costs S$10. After a S$2 unit tax, buyers pay S$11.20 and sellers keep S$9.20. What is the tax wedge?
2. What is the buyers’ burden per remaining unit?
3. What percentage of the per-unit tax wedge is borne by sellers in this example?
4. If 800 units are traded after the S$2 tax, what is tax revenue?
5. If demand is less price-elastic than supply, which side of the market tends to bear more of the tax?
6. Is tax revenue identical to the tax’s complete welfare effect?

Answers and why

1. 11.20 − 9.20 = S$2.00.
2. 11.20 − 10 = S$1.20.
3. (10 − 9.20) ÷ 2 × 100 = 40%.
4. 800 × S$2 = S$1,600.
5. Buyers, because they are relatively less responsive to the price change under the standard competitive model.
6. No. Changes in traded quantity, external costs or benefits and other market responses can affect total welfare.

Frequently asked questions

Does putting the tax on a business mean the business must bear all of it?

No. The legal remitter and economic bearers can differ. Prices and relative elasticities help explain the burden.

Can a tax be shared exactly 50–50?

Yes, a particular model or market may produce equal per-unit burdens. But an equal split should be calculated or justified, not assumed.

Does more inelastic demand mean a tax never reduces sales?

No. It means quantity demanded is relatively less responsive. Unless demand is perfectly inelastic in the specified model, some reduction in quantity may still occur.

Is a tax always harmful because it creates a wedge?

Not necessarily. A corrective tax may help account for an external harm. The full analysis must include the market failure and social benefits as well as private costs.

Keep learning with eduKateSG

Explore the How X Works Hub for the wider explanation of economics. Check these educational references: OpenStax — Elasticity and Pricing: Tax Incidence; OpenStax — Elasticity Key Concepts.

Quick Notes reminder: name the original price → find buyer price and seller receipt → calculate their differences from the original → compare elasticities → use actual new quantity for revenue. Who remits a tax is not necessarily who bears it.