potaxamnd

### 1) Overview
 The `potaxamnd` table serves as a historical repository for **Purchase Order Tax Amendments**. It tracks modifications made to tax percentages, duty codes, and sequences associated with specific Purchase Orders (`pono`) and specific amendment versions (`amndno`). This table is critical for auditing how tax structures evolved over the lifecycle of a procurement contract.
 
 ### 2) Column Dictionary
 
 | Column | Type | Nullable | Meaning | Allowed Values | SQL Usage |
 | :--- | :--- | :--- | :--- | :--- | :--- |
 | **index** | integer | NO | Primary key for the record. | e.g., 0, 1, 2 | `PK` |
 | **compcode** | string | NO | Unique identifier for the company/branch. | e.g., "DAS" | `JOIN`, `FILTER` |
 | **pono** | string | NO | Purchase Order Number. | e.g., "M7/RM/2013400036" | `JOIN`, `FILTER` |
 | **custcode** | string | NO | Customer or Vendor code associated with the PO. | e.g., "QHT(K)" | `JOIN` |
 | **srno** | integer | NO | Serial number/Sequence of the tax line item. | 1, 2, 3... | `ORDER BY` |
 | **duty_code** | integer | NO | Internal code identifying the type of tax or duty (GST, Excise, etc.). | e.g., 3, 7, 8 | `JOIN` |
 | **taxpercentage** | number | NO | The percentage rate applied for this specific duty. | e.g., 100.0, 12.0 | `MATH` |
 | **amndno** | integer | NO | The amendment version number for this specific record. | e.g., 3 | `JOIN`, `FILTER` |
 
 ### 3) Relationships & Join Map
 
 The `potaxamnd` table is a transactional child table designed to provide a specific "snapshot" of taxes for a given amendment version.
 
 #### Logical Joins:
 * **PO Header Amendments (`dbo.pohdramnd`)**: Join on `compcode`, `pono`, and `amndno` to retrieve general order status during that amendment.
 * **PO Detail Amendments (`dbo.podtlamnd`)**: Join on `compcode`, `pono`, and `amndno` to link taxes to specific amended line items.
 * **Current PO Taxes (`dbo.potax`)**: Join on `compcode` and `pono` to compare current tax rates against amended history.
 * **Duty Masters (`dbo.dutymas` or `dbo.cdutymas`)**: Join on `compcode` and `duty_code` to retrieve the human-readable name (e.g., "CGST") of the tax.
 * **Customer/Supplier (`dbo.cust` / `dbo.suppmas`)**: Join on `compcode` and `custcode` (or `supcode`) to get entity details.
 
 #### JOIN MAP (Authoritative):
 | Target Table | Join Column(s) | Likely/Real |
 | :--- | :--- | :--- |
 | `dbo.pohdramnd` | `compcode`, `PONO` (pono), `amndno` | **Real** |
 | `dbo.podtlamnd` | `compcode`, `pono`, `amndno` | **Real** |
 | `dbo.potax` | `compcode`, `pono`, `custcode`, `duty_code` | **Real** |
 | `dbo.dutymas` | `compcode`, `duty_code` | **Real** |
 | `dbo.cdutymas` | `compcode`, `duty_code` | **Real** |
 | `dbo.cust` | `compcode`, `custcode` | **Real** |
 
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