diff --git a/readme.md b/readme.md
index e347843..057f4ac 100644
--- a/readme.md
+++ b/readme.md
@@ -234,6 +234,139 @@ All requests follow a consistent pattern:
        → statusBupot = "CANCELLED-Done"
 ```
 
+## Happy Flow Diagram
+
+```mermaid
+flowchart TD
+    Start([Start]) --> Auth[Get Authentication Token]
+    Auth -->|POST /auth/gettoken| TokenAPI[Token API]
+    TokenAPI -->|Returns: access_token, idpel| TokenOK{Token Received?}
+    
+    TokenOK -->|Yes| Create[Create Tax Slip]
+    TokenOK -->|No| Error1[Check Credentials]
+    Error1 --> Auth
+    
+    Create --> CreateAPI{Choose Tax Slip Type}
+    CreateAPI -->|PPh 21| P21[POST /ifs/api/wit/bulanan/new]
+    CreateAPI -->|PPh A0| PA0[POST /ifs/api/wit/bulanan/new]
+    CreateAPI -->|PPh A1| PA1[POST /ifs/api/wit/tahunan/new]
+    
+    P21 -->|Request: monthlyIncome, dataBp21| CreateSuccess{Success?}
+    PA0 -->|Request: monthlyIncome, dataBpA0| CreateSuccess
+    PA1 -->|Request: yearlyIncome, dataBpA1| CreateSuccess
+    
+    CreateSuccess -->|Yes: status=1| Return1[Returns: nomorBupot, idBupot]
+    CreateSuccess -->|No: status=0| Error2[Handle Error]
+    Error2 --> Create
+    
+    Return1 --> Status[Check Tax Slip Status]
+    
+    Status --> StatusAPI{Choose Tax Slip Type}
+    StatusAPI -->|PPh 21| S21[POST /ifs/api/wit/status]
+    StatusAPI -->|PPh A0| SA0[POST /ifs/api/wit/status]
+    StatusAPI -->|PPh A1| SA1[POST /ifs/api/wit/status]
+    
+    S21 -->|Request: taxSlipVerification| StatusOK{Status Received?}
+    SA0 -->|Request: taxSlipVerification| StatusOK
+    SA1 -->|Request: taxSlipVerification| StatusOK
+    
+    StatusOK -->|statusBupot=NORMAL-DONE| Decision{What's Next?}
+    StatusOK -->|statusBupot=AMENDED| Decision
+    StatusOK -->|statusBupot=CANCELLED-Done| End1([End])
+    StatusOK -->|Error| Error3[Handle Error]
+    Error3 --> Status
+    
+    Decision -->|Download PDF| PDF[Download PDF]
+    Decision -->|Modify Slip| Edit[Edit Tax Slip]
+    Decision -->|Cancel Slip| Cancel[Cancel Tax Slip]
+    Decision -->|Done| End2([End])
+    
+    PDF --> PDFAPI{Choose Tax Slip Type}
+    PDFAPI -->|PPh 21| PF21[POST /ifs/api/wit/pdf]
+    PDFAPI -->|PPh A0| PFA0[POST /ifs/api/wit/pdf]
+    PDFAPI -->|PPh A1| PFA1[POST /ifs/api/wit/pdf]
+    
+    PF21 -->|Returns: Base64 PDF| PDFOK{Downloaded?}
+    PFA0 -->|Returns: Base64 PDF| PDFOK
+    PFA1 -->|Returns: Base64 PDF| PDFOK
+    
+    PDFOK -->|Yes| End3([End])
+    PDFOK -->|No| Error4[Handle Error]
+    Error4 --> PDF
+    
+    Edit --> EditAPI{Choose Tax Slip Type}
+    EditAPI -->|PPh 21| E21[POST /ifs/api/wit/bulanan/edit]
+    EditAPI -->|PPh A0| EA0[POST /ifs/api/wit/bulanan/edit]
+    EditAPI -->|PPh A1| EA1[POST /ifs/api/wit/tahunan/edit]
+    
+    E21 -->|Request: monthlyIncome, nomorBupot, idBupot| EditSuccess{Success?}
+    EA0 -->|Request: monthlyIncome, nomorBupot, idBupot| EditSuccess
+    EA1 -->|Request: yearlyIncome, nomorBupot, idBupot| EditSuccess
+    
+    EditSuccess -->|Yes: status=1| Return2[Returns: new nomorBupot, new idBupot]
+    EditSuccess -->|No: status=0| Error5[Handle Error]
+    Error5 --> Edit
+    
+    Return2 --> Status2[Check Status Again]
+    Status2 --> Status
+    
+    Cancel --> CancelAPI{Choose Tax Slip Type}
+    CancelAPI -->|PPh 21| C21[POST /ifs/api/wit/cancel]
+    CancelAPI -->|PPh A0| CA0[POST /ifs/api/wit/cancel]
+    CancelAPI -->|PPh A1| CA1[POST /ifs/api/wit/cancel]
+    
+    C21 -->|Request: taxSlipCancel| CancelSuccess{Success?}
+    CA0 -->|Request: taxSlipCancel| CancelSuccess
+    CA1 -->|Request: taxSlipCancel| CancelSuccess
+    
+    CancelSuccess -->|Yes: status=1| Return3[Returns: status=1]
+    CancelSuccess -->|No: status=0| Error6[Handle Error]
+    Error6 --> Cancel
+    
+    Return3 --> Status3[Verify Cancellation]
+    Status3 --> Status
+    
+    style Start fill:#e1f5fe
+    style Auth fill:#e1f5fe
+    style Create fill:#fff3e0
+    style Status fill:#e8f5e9
+    style PDF fill:#f3e5f5
+    style Edit fill:#fff8e1
+    style Cancel fill:#ffebee
+    style End1 fill:#c8e6c9
+    style End2 fill:#c8e6c9
+    style End3 fill:#c8e6c9
+    style Error1 fill:#ffcdd2
+    style Error2 fill:#ffcdd2
+    style Error3 fill:#ffcdd2
+    style Error4 fill:#ffcdd2
+    style Error5 fill:#ffcdd2
+    style Error6 fill:#ffcdd2
+```
+
+### Quick Reference: Happy Flow Steps
+
+| Step | Action | Endpoint | Returns |
+|------|--------|----------|---------|
+| 1 | Get Token | `POST /auth/gettoken` | `access_token`, `idpel` |
+| 2 | Create Slip | `POST /ifs/api/wit/bulanan/new` or `/tahunan/new` | `nomorBupot`, `idBupot` |
+| 3 | Check Status | `POST /ifs/api/wit/status` | `statusBupot` |
+| 4a | Download PDF | `POST /ifs/api/wit/pdf` | Base64 PDF |
+| 4b | Edit Slip | `POST /ifs/api/wit/bulanan/edit` or `/tahunan/edit` | New `nomorBupot` |
+| 4c | Cancel Slip | `POST /ifs/api/wit/cancel` | Success confirmation |
+
+### Status Flow
+
+```mermaid
+stateDiagram-v2
+    [*] --> NORMAL_DONE: Pengesahan (New)
+    NORMAL_DONE --> AMENDED: Penggantian (Edit)
+    AMENDED --> AMENDED: Penggantian Lagi
+    NORMAL_DONE --> CANCELLED_DONE: Pembatalan (Cancel)
+    AMENDED --> CANCELLED_DONE: Pembatalan (Cancel)
+    CANCELLED_DONE --> [*]
+```
+
 ## Important Notes
 
 1. **Language**: All API documentation and field names are in Indonesian (Bahasa Indonesia)