Add comprehensive EU transaction handling for CA-3 VAT declarations

EU Transaction Scenarios:
1️⃣ Incoming EU Invoices (Purchases):
- Supplier invoices HT (no VAT)
- French autoliquidation: 4452xxx (VAT due) + 4456xx (VAT deductible)
- Net effect: zero if fully deductible
- CA-3 impact: Lines 17 (VAT due) + 20/21 (VAT deductible)

2️⃣ Outgoing EU Invoices (Sales):
- Case A (B2B): No French VAT, Lines 05/06 (base HT only)
- Case B (B2C): OSS threshold handling (€10,000)
- Case C (Special): Construction/energy reverse charge
- Invoice text requirements for EU transactions

3️⃣ DEB/DES Integration:
- Link CA-3 lines 05/06 with exchange declarations
- Cross-validation between CA-3 and DEB/DES
- Automatic data import and validation

Enhanced Features:
- EU transaction type detection and classification
- OSS threshold monitoring and alerts
- DEB/DES data integration and validation
- Special case handling (construction, energy)
- Comprehensive EU transaction workflow

Updated estimates: +64 hours for EU transaction handling
Total project: 414+ hours with full EU compliance

PLANNING.md

@@ -29,6 +29,14 @@ The module handles the complete French CA-3 VAT declaration structure:
 | **B3** | Répartition 5,5% (base + taxe) | 5.5% VAT operations (base + VAT) | 7xxxx → 44573x | Reduced rate operations |
 | **B4** | Répartition 2,1% (base + taxe) | 2.1% VAT operations (base + VAT) | 7xxxx → 44574x | Reduced rate operations |
 
+##### A. Opérations intracommunautaires (Intra-EU Operations)
+
+| CA-3 Line | Label | Description | PCG Accounts | Form Mapping |
+|-----------|-------|-------------|---------------|--------------|
+| **05** | Livraisons intracommunautaires (B2B) | Intra-EU sales to businesses (no French VAT) | 7xxxx (EU sales) | Base HT only, no VAT |
+| **06** | Prestations intracommunautaires (B2B) | Intra-EU services to businesses (no French VAT) | 7xxxx (EU services) | Base HT only, no VAT |
+| **B2C** | Ventes B2C intracommunautaires | Intra-EU sales to individuals (French VAT) | 7xxxx → 4457xx | Normal French VAT rules |
+
 ##### B. TVA due (VAT Due)
 
 | CA-3 Line | Label | Description | PCG Accounts | Form Mapping |
@@ -50,6 +58,40 @@ The module handles the complete French CA-3 VAT declaration structure:
 | **28** | TVA nette à payer | Net VAT to pay | 445510 | If due > deductible |
 | **29** | Crédit de TVA à reporter ou remboursement | VAT credit to carry forward or refund | 445670 | Credit amount |
 
+### EU Transaction Handling
+
+#### 1️⃣ Incoming Invoices (EU Purchases)
+- **Scenario**: Supplier in another EU country invoices HT (no VAT)
+- **French Treatment**: Self-assess VAT (autoliquidation)
+- **Accounting**: Book both VAT due (4452xxx) and VAT deductible (44566x/44562x)
+- **Net Effect**: Zero if fully deductible
+- **CA-3 Impact**: Line 17 (VAT due) and Lines 20/21 (VAT deductible)
+
+#### 2️⃣ Outgoing Invoices (EU Sales)
+
+##### Case A: B2B Intra-EU Sales (Business Customers)
+- **Invoice Treatment**: No French VAT charged
+- **Invoice Text**: "Exonération de TVA, article 138" (goods) or "Autoliquidation par le preneur, article 196" (services)
+- **Accounting**: No 4457xxx VAT output booked
+- **CA-3 Declaration**: Lines 05/06 (base HT only, no VAT)
+- **Additional**: DEB/DES declarations required
+
+##### Case B: B2C Intra-EU Sales (Individual Customers)
+- **Under OSS Threshold (€10,000)**: Charge French VAT (4457xx)
+- **Over OSS Threshold**: Register for OSS/IOSS, charge customer's country VAT rate
+- **CA-3 Declaration**: Normal French VAT rules or OSS portal
+
+##### Case C: Special Reverse Charge Cases
+- **Construction Services**: Subcontractor invoices HT, contractor self-assesses
+- **Energy Products**: Specific reverse charge rules
+- **Accounting**: Similar to EU purchases (4452xxx + 4456xx)
+
+#### 3️⃣ DEB/DES Integration
+- **DEB (Déclaration d'échanges de biens)**: Goods movement declarations
+- **DES (Déclaration d'échanges de services)**: Services movement declarations
+- **Integration**: Link CA-3 lines 05/06 with DEB/DES data
+- **Validation**: Cross-check amounts between CA-3 and DEB/DES
+
 ## Technical Requirements
 
 ### Database Structure

TASK.md

@@ -159,6 +159,21 @@
   - **Estimated**: 10 hours
   - **Dependencies**: Task 3.1.5
 
+- [ ] **Task 3.1.7**: Implement EU transaction handling
+  - Incoming EU invoices: autoliquidation (4452xxx + 4456xx)
+  - B2B EU sales: no French VAT, lines 05/06 (base HT only)
+  - B2C EU sales: OSS threshold handling (€10,000)
+  - Special cases: construction, energy reverse charge
+  - **Estimated**: 15 hours
+  - **Dependencies**: Task 3.1.5
+
+- [ ] **Task 3.1.8**: Add DEB/DES integration
+  - Link CA-3 lines 05/06 with DEB/DES data
+  - Cross-validation between CA-3 and exchange declarations
+  - Automatic DEB/DES data import
+  - **Estimated**: 12 hours
+  - **Dependencies**: Task 3.1.7
+
 ### 3.2 Period Management
 - [ ] **Task 3.2.1**: Implement period calculation
   - Automatic period detection
@@ -449,16 +464,16 @@
 - Performance optimization for large datasets
 - Security considerations for financial data
 
-## Total Estimated Time: 350+ hours
+## Total Estimated Time: 414+ hours
 
 ### Breakdown by Phase:
 - **Phase 1-2**: Foundation & Configuration (40 hours)
-- **Phase 3**: Data Processing (50 hours) 
+- **Phase 3**: Data Processing (87 hours) 
 - **Phase 4**: User Interface (30 hours)
 - **Phase 5**: Export & Reporting (25 hours)
 - **Phase 6**: Testing & Documentation (25 hours)
 - **Phase 7**: Advanced Features (80 hours)
-- **Buffer & Integration**: 100 hours
+- **Buffer & Integration**: 127 hours
 
 ## Priority Order:
 1. Database schema and core classes

langs/en_US/declarationtva.lang

@@ -71,6 +71,25 @@ DECLARATIONTVA_LINE_28_TOOLTIP = Net VAT to pay if due > deductible
 DECLARATIONTVA_LINE_29 = Line 29 - VAT credit to carry forward or refund
 DECLARATIONTVA_LINE_29_TOOLTIP = Amount of VAT credit to carry forward or request refund
 
+# Intra-EU Operations
+DECLARATIONTVA_LINE_05 = Line 05 - Intra-EU deliveries (B2B)
+DECLARATIONTVA_LINE_05_TOOLTIP = Intra-EU B2B sales (base HT only, no VAT)
+DECLARATIONTVA_LINE_06 = Line 06 - Intra-EU services (B2B)
+DECLARATIONTVA_LINE_06_TOOLTIP = Intra-EU B2B services (base HT only, no VAT)
+
+# EU Transaction Management
+DECLARATIONTVA_EU_PURCHASES = Intra-EU purchases
+DECLARATIONTVA_EU_SALES_B2B = Intra-EU B2B sales
+DECLARATIONTVA_EU_SALES_B2C = Intra-EU B2C sales
+DECLARATIONTVA_EU_AUTOLIQUIDATION = Intra-EU autoliquidation
+DECLARATIONTVA_EU_REVERSE_CHARGE = Reverse charge by customer
+DECLARATIONTVA_EU_EXONERATION = VAT exemption
+DECLARATIONTVA_EU_OSS_THRESHOLD = OSS threshold (€10,000)
+DECLARATIONTVA_EU_OSS_REGISTRATION = OSS/IOSS registration
+DECLARATIONTVA_EU_DEB_DES = DEB/DES (Exchange declarations)
+DECLARATIONTVA_EU_CONSTRUCTION = Construction services
+DECLARATIONTVA_EU_ENERGY = Energy products
+
 # VAT Rates
 DECLARATIONTVA_RATE_20 = Rate 20%
 DECLARATIONTVA_RATE_10 = Rate 10%

langs/fr_FR/declarationtva.lang

@@ -53,6 +53,25 @@ DECLARATIONTVA_LINE_28_TOOLTIP = TVA nette à payer si due > déductible
 DECLARATIONTVA_LINE_29 = Ligne 29 - Crédit de TVA à reporter ou remboursement
 DECLARATIONTVA_LINE_29_TOOLTIP = Montant du crédit de TVA à reporter ou demander remboursement
 
+# Opérations intracommunautaires
+DECLARATIONTVA_LINE_05 = Ligne 05 - Livraisons intracommunautaires (B2B)
+DECLARATIONTVA_LINE_05_TOOLTIP = Ventes intracommunautaires B2B (base HT uniquement, pas de TVA)
+DECLARATIONTVA_LINE_06 = Ligne 06 - Prestations intracommunautaires (B2B)
+DECLARATIONTVA_LINE_06_TOOLTIP = Services intracommunautaires B2B (base HT uniquement, pas de TVA)
+
+# Gestion des transactions UE
+DECLARATIONTVA_EU_PURCHASES = Achats intracommunautaires
+DECLARATIONTVA_EU_SALES_B2B = Ventes intracommunautaires B2B
+DECLARATIONTVA_EU_SALES_B2C = Ventes intracommunautaires B2C
+DECLARATIONTVA_EU_AUTOLIQUIDATION = Autoliquidation intracommunautaire
+DECLARATIONTVA_EU_REVERSE_CHARGE = Autoliquidation par le preneur
+DECLARATIONTVA_EU_EXONERATION = Exonération de TVA
+DECLARATIONTVA_EU_OSS_THRESHOLD = Seuil OSS (10 000 €)
+DECLARATIONTVA_EU_OSS_REGISTRATION = Inscription OSS/IOSS
+DECLARATIONTVA_EU_DEB_DES = DEB/DES (Déclarations d'échanges)
+DECLARATIONTVA_EU_CONSTRUCTION = Services de construction
+DECLARATIONTVA_EU_ENERGY = Produits énergétiques
+
 # Taux de TVA
 DECLARATIONTVA_RATE_20 = Taux 20%
 DECLARATIONTVA_RATE_10 = Taux 10%