retsrnduty

### 1) Overview
 The `retsrnduty` table is a transaction-level detail table that stores the breakdown of specific duties and taxes associated with a **Material Receipt Number (mrpno)** during a return process (likely "Return - Store Receipt Note"). It maps specific tax identifiers (`duty_code`) to their calculated monetary values for a particular receipt.
 
 ### 2) Column Dictionary
 | Column | Type | Nullable | Meaning | Allowed Values | SQL Usage |
 | :--- | :--- | :--- | :--- | :--- | :--- |
 | **index** | integer | No | Primary Key (Internal/Identity) | | Unique identifier for the row |
 | **compcode** | string | No | Company Code | e.g., "DAS" | `WHERE compcode = 'DAS'` (Join Key) |
 | **mrpno** | integer | No | Material Receipt Purchase Number | e.g., 2 | Join to MRN/Receipt headers |
 | **duty_code** | integer | No | Unique identifier for a specific tax/duty type | 1, 10, 17, 2, 21 | Join to `dutymas` or `cdutymas` |
 | **amount** | number | No | Monetary value of the specific duty | | `SUM(amount)` for total tax |
 
 ### 3) Relationships & Join Map
 
 #### Logical Parents (Strict Joins)
 * **dbo.dutymas** or **dbo.cdutymas**: Joined via `duty_code` and `compcode` to retrieve the name and percentage of the tax (e.g., GST, Excise).
 * **dbo.cmrrhdr** (Material Receipt Header): Joined via `mrpno` and `compcode` to identify the vendor or date associated with the original receipt.
 * **dbo.srnduty**: Likely a sister table for non-return receipt duties.
 
 #### Potential Joins (Likely)
 * **dbo.rmincoming**: Joined via `mrpno` and `compcode` to access raw material incoming inspection and billing data.
 * **dbo.cmrrduty**: Related table containing similar duty structures for current material receipts.