# Vendor Payment Diff Amount - Version 2.0

## Overview

This module extends Odoo 17's vendor payment functionality to support **multiple payment deductions** such as withholding tax, payment fees, and other charges.

## Version 2.0 Changes

### Major Update: One2Many Deduction Lines

Version 2.0 introduces a significant architectural change:

**Before (v1.x):**
- Single deduction amount field (`amount_substract`)
- Single deduction account field (`substract_account_id`)
- One payment could have only one deduction

**After (v2.0):**
- Multiple deduction lines (`deduction_line_ids`)
- Each deduction line has its own amount and account
- One payment can have multiple deductions with different accounts
- Total deductions computed automatically

### Migration Notes

**Important:** This is a breaking change. Existing payments with deductions will need to be migrated.

If you have existing payments with `amount_substract` and `substract_account_id` values, you should:

1. Backup your database before upgrading
2. After upgrade, existing single deductions will need to be manually converted to deduction lines
3. The old fields (`amount_substract`, `substract_account_id`) are now computed/removed

### New Features

1. **Multiple Deduction Lines**: Add as many deduction lines as needed to a single payment
2. **Individual Descriptions**: Each deduction can have its own description
3. **Flexible Sequencing**: Reorder deduction lines using drag-and-drop
4. **Automatic Totals**: Total deductions calculated automatically
5. **Batch Payment Support**: Deduction lines work seamlessly with batch payments

## Usage

### ⚠️ IMPORTANT: Expense Account Required

**When using payment deductions, you MUST set the Expense Account field first.**

### Creating a Payment with Deductions

1. Go to Accounting > Vendors > Payments
2. Create a new outbound payment
3. **⚠️ CRITICAL: Set the Expense Account field** (e.g., "Telepon & Internet")
4. Enter the payment amount
5. In the "Deductions" section, add one or more deduction lines:
   - Select the deduction account (e.g., PPh 21 - Withholding Tax)
   - Enter the deduction amount
   - Optionally add a description
6. The "Total Deductions" and "Final Payment Amount" are calculated automatically
7. Post the payment

**Note:** If you try to add deductions without setting the Expense Account, you will get a validation error.

### Journal Entry Structure

For a payment of 2000 with two deductions (100 for tax, 50 for fees):

```
Expense/Payable Account    Debit: 2000   (original amount)
Tax Account (PPh 21)       Credit: 100   (first deduction)
Fee Account (PPh 29)       Credit: 50    (second deduction)
Bank Account               Credit: 1850  (final payment amount)
---
Total: Debit 2000 = Credit 2000 (balanced)
```

### Batch Payments

When using with `vendor_batch_payment_merge`:

1. Create a batch payment
2. Add payment lines
3. For each line, add deduction lines in the form view
4. Generate payments - deductions are automatically transferred

## Technical Details

### New Models

- `payment.deduction.line`: Stores individual deduction lines

### Modified Models

- `account.payment`: Added `deduction_line_ids` (One2many)
- `account.batch.payment.line`: Added `deduction_line_ids` (One2many)

### Fields

**Payment Deduction Line:**
- `sequence`: Order of deduction lines
- `substract_account_id`: Account for this deduction (required)
- `amount_substract`: Deduction amount (required)
- `name`: Optional description
- `payment_id`: Link to payment
- `batch_payment_line_id`: Link to batch payment line

**Account Payment:**
- `deduction_line_ids`: One2many to deduction lines
- `amount_substract`: Computed total of all deductions
- `final_payment_amount`: Computed (amount - total deductions)

## Requirements

- Odoo 17.0
- `account` module
- `vendor_batch_payment_merge` module

## License

LGPL-3

## Author

Suherdy Yacob