# Progressive scale by brackets

## Intention

I want to apply the higher rate only to the amount above the threshold.

The example pins 100 KZT at the threshold and 200 KZT on a 1500 base, not 300 KZT.

## Incorrect form and why it stays silent

```law title="Incorrect form"
decision Levy(x: Money) -> Money { table hit first { when x <= 1000 KZT => x * 10 percent; } }
```

Without otherwise the table does not define an outcome outside the first row: a static rejection. Progression also needs the accumulated amount of the lower bracket; otherwise the higher rate is applied to the whole base.

## Correct form

```law
language "law.core" version "0.2";
package recipes.l.r02 version "0.1.0";
namespace "urn:recipe:l-calc:02";

decision Levy(x: Money) -> Money {
    table hit first {
        when x <= 1000 KZT => x * 10 percent;
        otherwise => 100 KZT + (x - 1000 KZT) * 20 percent;
    }
}
```

## Frozen execution scene

| Facts and choice | Question | Answer |
|---|---|---|
| 1. base 0 KZT | `Levy(0 KZT)` | `0 KZT` / `COMPUTED` |
| 2. base 999 KZT | `Levy(999 KZT)` | `99.9 KZT` / `COMPUTED` |
| 3. base 1000 KZT | `Levy(1000 KZT)` | `100 KZT` / `COMPUTED` |
| 4. base 1500 KZT | `Levy(1500 KZT)` | `200 KZT` / `COMPUTED` |

```law
test "zero base, zero levy" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00+05:00;
            knowledge_time @2026-09-13T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        
    }
    evaluate Levy(0 KZT);
    expect value == 0 KZT;
    expect evaluation_status == COMPUTED;
    
}
```

```law
test "base below break" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00+05:00;
            knowledge_time @2026-09-13T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        
    }
    evaluate Levy(999 KZT);
    expect value == 99.9 KZT;
    expect evaluation_status == COMPUTED;
    
}
```

```law
test "base at break" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00+05:00;
            knowledge_time @2026-09-13T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        
    }
    evaluate Levy(1000 KZT);
    expect value == 100 KZT;
    expect evaluation_status == COMPUTED;
    
}
```

```law
test "base above break" {
    given {
        context {
            legal_time @2026-09-13;
            decision_time @2026-09-13T09:00:00+05:00;
            knowledge_time @2026-09-13T09:00:00+05:00;
            timezone "Asia/Almaty";
        }
        
    }
    evaluate Levy(1500 KZT);
    expect value == 200 KZT;
    expect evaluation_status == COMPUTED;
    
}
```



## Counterfactual

Mutation: `        otherwise => 100 KZT + (x - 1000 KZT) * 20 percent;` → ``; expected `LDC-E8304`. Additional counterfactuals are shown as separate table rows.

## Boundary

A teaching non-negative base and conventional rates. Row order is semantic; a single rate on the whole base does not yield a progressive sum. A calculator shared by several rules lives in a separate recipe.

## Pitfall

Without the accumulated lower-bracket amount, the higher rate would apply to the whole base: 300 KZT instead of 200 KZT on a 1500 base.