tradon/modules/purchase_trade/docs_source/business/fees.en.md

# Fees

Language: `en`
Mirror page: [fees.md](fees.md)
Status: `partial migration`

See also the historical technical page: `../fees.md`.

> **Operational summary**
> A fee carries an amount, but its quantity must remain aligned with the lots
> it applies to. `Per packing` is the only exception: it follows packing units,
> not lot weight.

| Marker | Topic | Short rule |
| --- | --- | --- |
| Quantity | `fee.quantity` | Sum of linked lots in `fee.lots`. |
| State | empty `fee.qt_state` | Uses the contract `weight basis`. |
| State | filled `fee.qt_state` | Uses that state, capped by the `weight basis`. |
| Fallback | state missing on lot | Uses the closest previous state by `sequence`. |
| Net / gross | `fee.weight_type` | `net` reads `quantity`, `brut` reads `gross_quantity`. |
| Packing | `ppack` | Packing quantity, decoupled from weight. |
| Control | Python + SQL | Application guard and SQL diagnostic. |

## Consultant Rules

### BR-PT-FEE-001 - Freight value from shipment fee

Source: `BR-PT-003`

#### Consultant Rule

The freight value printed on invoice documents comes from the maritime freight
fee on the shipment, not from a direct invoice field.

#### Developer Notes

- Find the physical lot from the invoice.
- Find its `shipment_in`.
- Search the `fee.fee` with `product.name = 'Maritime freight'`.
- Use `fee.get_amount()`.

### BR-PT-FEE-002 - Effective lots for fees

Source: `BR-PT-021`

#### Consultant Rule

A fee follows the virtual lot until a physical lot is linked. As soon as a
physical lot is linked, physical lots become the calculation basis for the fee.

#### Developer Notes

- Do not remove the virtual lot link: it remains the fallback.
- Effective lots are:
  - physical lots if at least one physical lot is linked;
  - otherwise virtual lots.
- The same selection applies to fee PnL.
- Synchronization points:
  - fee creation;
  - `fee.lots` link;
  - `quantity_theorical` change;
  - weighing;
  - physical lot removal.

### BR-PT-FEE-003 - Fee quantity

#### Consultant Rule

The quantity of a fee follows the quantity life cycle of its linked lots. It
must represent the sum of those lots in the authorized contractual quantity
state.

#### Short Rule

```text
fee.quantity = sum(applicable quantity of effective fee.lots)
```

#### Quantity State Selection

| Case | Target state |
| --- | --- |
| empty `fee.qt_state` | `weight basis` of the fee carrier contract |
| filled `fee.qt_state` | `fee.qt_state`, unless later than the `weight basis` |
| `fee.qt_state` later than `weight basis` | `weight basis` |
| target state missing on lot | closest previous state by `lot.qt.type.sequence` |
| no target state available | current lot weight, only when no `weight basis` applies |

#### Weight Basis Source

| Fee | `weight basis` |
| --- | --- |
| Purchase fee | `fee.line.purchase.wb.qt_type` |
| Sale fee | `fee.sale_line.sale.wb.qt_type` |
| Shipment fee | purchase weight basis of the lot when present |
| Shipment fee without purchase | sale weight basis of the lot when present |

#### Net / Gross

- If `fee.weight_type = net`:
  - read `lot.qt.hist.quantity`.
- If `fee.weight_type = brut`:
  - read `lot.qt.hist.gross_quantity`.

#### Per Packing

- `mode = ppack` is excluded from the weight rule.
- `fee.quantity` represents a packing quantity.
- This quantity may be decoupled from net or gross weight.

#### Lump Sum

- `mode = lumpsum` also follows the quantity rule.
- The amount remains fixed.
- The quantity gives a more accurate per-ton price.

### BR-PT-FEE-004 - `% rate` fees from financing delta

Source: historical `BR-PT-016` and `2026-04-30` notes

#### Consultant Rule

Percentage financial fees are calculated with the financing delta from the
`BL date` estimated line, not with the current date.

#### Developer Notes

- Formula: `amount = unit_price * quantity * (price / 100) * fin_int_delta / 360`.
- Delta source: `Estimated date` line with `trigger = bldate`.
- If no `bldate` line exists, do not calculate a `% rate` amount.

## Developer Section

### Key Fields

- Fee: `fee.fee`
- Fee lots: `fee.lots`
- Fee quantity: `fee.fee.quantity`
- Mode: `fee.fee.mode`
- Optional quantity state: `fee.fee.qt_state`
- Net / gross: `fee.fee.weight_type`
- Lot quantity state: `lot.qt.hist.quantity_type`
- Net quantity: `lot.qt.hist.quantity`
- Gross quantity: `lot.qt.hist.gross_quantity`
- State order: `lot.qt.type.sequence`
- Purchase / sale weight basis: `purchase.weight.basis.qt_type`

### Calculation Functions

- `Fee._get_effective_fee_lots()`:
  - selects physical lots, then virtual lots.
- `Fee._target_qt_type_for_lot()`:
  - chooses `fee.qt_state` or the `weight basis`;
  - caps the state at the `weight basis`.
- `Fee._select_lot_qt_type()`:
  - takes the exact state when it exists;
  - otherwise takes the closest previous state by `sequence`.
- `Fee._get_lot_fee_quantity()`:
  - reads net or gross depending on `weight_type`.
- `Fee.sync_quantity_from_lots()`:
  - resynchronizes `fee.quantity`.

### Python Guards

- Central check:
  - `fee.fee.assert_quantity_consistency()`
  - `fee.fee.assert_quantities_consistency()`
- Trigger points:
  - fee creation;
  - fee modification;
  - `fee.lots` creation / modification / deletion;
  - weighing through linked fee resynchronization.
- Exception:
  - `mode = ppack` is not controlled as weight.

### Known Gap

- Lot split / merge:
  - the workflow may clone or create physical lots;
  - rewiring `fee.lots` to the new lots is not guaranteed yet;
  - affected fees must therefore be checked with the SQL diagnostic after this
    workflow is used.

### SQL Diagnostic

- Script:
  - [sql/fee_quantity_consistency_checks.sql](sql/fee_quantity_consistency_checks.sql)
- Usage:
  - audit test databases;
  - audit historical data;
  - qualify data before correction.
- The script returns non-`ppack` fees where `fee.quantity` does not match the
  sum of effective lots according to the applicable quantity state.