Is there a standardized way to express discounts or credits in an order summary?


Sub total: $20
Discount:  -$10
Total:     $10

I've seen discounts expressed as -$10, $-10, ($10), and +$10.

Are any of these expressions more "correct" than the other? Is there a common or standardized way to express discounts? Where would these standards be documented?



"-$10" is about as clear as it gets.

Talk like your users

Ask yourself how most people write out a subtraction problem?
The discount in your example is "subtract ten dollars".
Write it like any normal person would: $20 -$10 = $10

($10) is for accountants. Normal people don't write their numbers that way. And an accountant will have no trouble figuring out -$10.

+$10 makes no sense whatsoever: "$20 + ($10 discount) = $10" is really going to make users scratch their head.

$-10 is just weird. Is there a standard where denomination comes before the operator?

Try it out

Prototype a simple checkout workflow and see if it confuses anyone. Then you'll have some data before you throw it out in the wild.

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