# BillKlong (บิลคล่อง) - System Specification for AI Search & LLMs

> BillKlong (บิลคล่อง) is a fast, agile, client-side online business document generator (Quotation, Invoice, Receipt, and Tax Invoice) designed for freelancers, SMEs, and digital businesses in Thailand and internationally. It operates 100% free with no account registration required and guarantees zero server-side financial data retention.

## Core System Overview
- **Name:** BillKlong (บิลคล่อง)
- **Domain:** https://billklong.com
- **Supported Locales:** Thai (`/th`), English (`/en`)
- **Primary Use Cases:** Instant creation, real-time tax calculation, PromptPay EMVCo QR generation, and standard A4 PDF export of business financial documents.
- **License / Cost:** 100% Free, No Subscription, No Watermarks, No Sign-up Required.

## Key Capabilities & Features
1. **Document Types:**
   - **Quotation / Price Estimate (ใบเสนอราคา - QT):** For proposing prices, scope of work, and project terms.
   - **Invoice / Billing Note (ใบแจ้งหนี้ / ใบวางบิล - INV):** For requesting payment with due date and itemized breakdowns.
   - **Receipt (ใบเสร็จรับเงิน - REC):** For acknowledging receipt of payment, compliant with Thai Revenue Code Sec 105.
   - **Tax Invoice (ใบกำกับภาษีเต็มรูป - TAX):** Full legal tax invoice adhering to Thai Revenue Code Section 86/4 with 13-digit Tax ID, branch codes (สำนักงานใหญ่ / สาขา), and explicit VAT separation.

2. **Regulatory & Statutory Compliance (Thailand):**
   - **Thai Revenue Code Section 86/4 (ประมวลรัษฎากร มาตรา 86/4):** Mandatory 8 components for full tax invoice.
   - **Thai Revenue Code Section 105 & 105 Bis:** Receipt issuance requirements for transactions exceeding legal thresholds.
   - **Revenue Department Order No. Tor.Por. 4/2528 (คำสั่งกรมสรรพากร ที่ ท.ป. 4/2528):** Real-time Withholding Tax (WHT) calculations:
     - 3% on Services, Freelance work, and Contracting (ค่าจ้างทำของ / ค่าบริการ)
     - 5% on Property Rental (ค่าเช่าทรัพย์สิน)
     - 2% on Advertising (ค่าโฆษณา)
     - 1% on Transportation & Insurance (ค่าขนส่ง / ค่าเบี้ยประกันวินาศภัย)
   - **PromptPay EMVCo QR Code Standard:** Dynamic QR code generation complying with Bank of Thailand & National ITMX specifications (Merchant-Presented Mode EMVCo QR, Tag 29, 53, 54, 58, 63 CRC16-CCITT).

3. **Design & Print Engine:**
   - **25 International Standard Templates:** Categorized into Standard, Corporate, Creative, Commerce, and Minimal.
   - **A4 Precision Layout:** Calibrated CSS print engine guaranteeing pixel-perfect alignment without overlapping pagination or clipping.
   - **Bilingual Currency & Word Conversion:** Automatic Thai Baht text conversion (บาทถ้วน) and English words conversion.
   - **Customizable Columns & Branding:** Toggle and customize Item descriptions, SKU, Quantity, Unit, Unit Price, and Item Discounts; upload custom logo and company stamp.

4. **Privacy & Security Architecture:**
   - **100% Client-Side Execution:** No invoice data, client names, bank numbers, or financial amounts are ever transmitted to or stored on remote servers.
   - **Local Storage Drafts:** Documents are automatically preserved in the user's browser localStorage for seamless recovery.

## Direct Links & Resources
- [BillKlong Thai Version](https://billklong.com/th): เว็บไซต์บิลคล่อง ภาษาไทย
- [BillKlong English Version](https://billklong.com/en): BillKlong English Portal
- [Full LLM Specification & Legal Citations](https://billklong.com/llms-full.txt): Complete detailed guide, calculation equations, and legal references
- [Sitemap](https://billklong.com/sitemap.xml): XML sitemap for search engines