The duty and the prize: two directions

A single published rules document can round one number up and another down, and the two directions are both defensible while producing the same one-way flow. This page puts a duty and a prize side by side.

Open the partner account What rounding cannot do

Sample spec

stakes: 5
prizes: 3
duty: 15%
collected: 0.0335

the unitThe smallest amount the currency can express. In a two-decimal currency it is 0.01; the increment a stake must take is coarser and published per market.

the directionWhich way each rounding goes: down on a stake and a return, up on a duty and down on a prize. It is a rule, published, and it decides who keeps the fraction.

the volumeOne unit per event is nothing once and a figure at scale: on the samples, two thousand events of the same size retain 60.00 from the digits alone.

Direct answer

A duty is charged on the stake and rounded up to the unit, so it never under-collects; a prize is rounded down to the unit, so it never over-pays. On five invented stakes and three prizes from one rules document, the two directions collected 0.0335 between them, and neither rounding was a fee: each was simply the direction the rule chose.

Five stakes, three prizes

Both directions are ordinary in published rules. Read together, they are the clearest example of a point that is otherwise easy to miss: the direction of a rounding is a rule, and the same document can set it one way on the amount charged and the other way on the amount paid.

Sample G - a 15% duty rounded up on five stakes
Stake	Exact duty	Charged	Excess
10.00	1.5000	1.50	0.0000
10.05	1.5075	1.51	0.0025
3.33	0.4995	0.50	0.0005
1.01	0.1515	0.16	0.0085
0.10	0.0150	0.02	0.0050
24.49	3.6735	3.69	0.0165

Sample G - three prizes rounded down on the same document
Exact prize	Paid	Retained
12.345	12.34	0.005
7.999	7.99	0.009
3.333	3.33	0.003
23.677	23.66	0.017

sample G - both directions in one figure duty rounded up: 3.69 - 3.6735 = 0.0165 more collected prizes rounded down: 23.677 - 23.66 = 0.0170 less paid the two together = 0.0165 + 0.0170 = 0.0335 in the house's favour across 8 events - from two rules that are each individually defensible.

The narrow point, and the wide one

The narrow point is that a 15% duty rounded up is not a 15% duty: on a stake of 0.10 it is 20% and on a stake of 10.00 it is exactly 15%. That is the same fixed-cost-per-event pattern as the conversion page, and it is worth seeing twice because the two cases look unrelated. The wide point is that a player who checks only the percentage, only the headline, or only one side of the equation will not see the direction at all. Both roundings are stated in the rules; neither is hidden; and the reason the sample exists is that a rule's direction is a fact the reader can find rather than a suspicion they have to carry.

Read the duty's rounding direction: rounded up on a small stake can be several percentage points above the headline rate.
Read the prize's rounding direction separately; the two do not have to match and on sample G they did not.
On a very small stake, check whether the minimum duty exceeds the stake's own fraction - a 0.10 stake carried 0.02 of duty on sample G.
Do not assume the duty applies to the return rather than the stake; read which figure it is charged on.
Where a prize can be paid in more than one form, remember each form carries its own rounding.

The duty and the prize: two directions

Five stakes, three prizes

The narrow point, and the wide one

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