Own integration with the State Tax Service's cash register system

Welcome! We are a team of developers with 4 years of experience in process automation for e-commerce and commercial data protection. We have a great understanding of the specifics of direct interaction with the Tax API and are ready to implement a reliable custom PRRO tailored to your needs. We will ensure instant signing of electronic receipts, uninterrupted offline mode, and complete security for storing tokens and certificates on your server. The system will operate stably, quickly, and without monthly subscription fees to third-party services. We are ready to start discussing the technical task in private messages right now.

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Welcome! Our team has been specializing in complex backend development, integration of third-party services, and data protection for 4 years. We are ready to develop a fully autonomous integration module with the free fiscal server of the State Tax Service without any intermediaries. We will write clean code for generating correct XML or JSON packages, configure server-side KEP overlay, and automate the entire cycle: opening changes, generating receipts, sending X and Z reports. Special attention will be paid to the architecture of the offline mode with clear control of time limits and number ranges according to legislative requirements. Write to us, and we will discuss the architecture of your system and agree on the development stack.

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Hello! I have reviewed the task. The project is quite serious, as it involves not only integration but also stable operation with fiscalization, offline modes, digital signatures, queues, and interaction with the tax service without data loss.

I have experience in full-stack development of commercial systems and integrations through API / Webhooks / SDK, so I understand the requirements for such solutions well: reliability, queues, error handling, signatures, synchronization, and fault tolerance.

I can:
• implement the backend part in Laravel
• create a UI for working with digital signatures, cash registers, and cashiers
• set up integration with the tax service
• implement offline/online logic and fiscalization queues
… • integrate the frontend application for POS through SDK events/actions
• ensure stable synchronization through API/Webhooks

I work with both backend and frontend parts, so I can manage the task comprehensively without a gap between teams.

About myself:
• 5 years of freelance development
• experience with production systems, financial logic, and complex integrations
• stack: Laravel, TypeScript, Next.js, Node.js, PostgreSQL, WebSocket/API integrations

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I have my own operational cross-platform PRRO - offline/online mode. The only thing is that it’s not quite your format - it’s in Java and works as a microservice/receives XML receipts from the POS system.

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My name is Vladislav. I don't like to talk much about myself and what I do. I prefer to show it once. But briefly.

What I have done myself and it is currently working:

- Cash register program for Windows (fiscalization via Checkbox, offline for up to 36 hours, X/Z reports, returns, digital signature)
- Web dashboard for the manager (monitoring 26 cash registers in real-time, analytics, access levels)
- Mobile application (PWA) for the owner - sees all points from the phone, prints X/Z reports to the cash printer remotely, takes cash from the cash register at the register
- Loyalty program - bonuses, levels (Bronze, Silver, Gold), coupons, linking the customer at the register by phone
- Own discount and promotion engine (product groups, price by quantity, promo codes, Wheel of Fortune, Auction, referral program)
… - Telegram bot for customers (electronic receipts, personal account, loyalty barcode, promotions, notifications about new points)
- Telegram bot for the manager with auto-reports (reconciliation with the bank terminal to the penny, sales analysis, anomalies)
- Cash log analyzer with AI - automatically detects suspicious actions of cashiers (price manipulations, atypical cancellations, sales outside shifts) and provides the manager with a morning report
- Remote cash register management bot - from the phone I can take a screenshot of any cash register, lock the screen, send a message to the cashier, synchronize the catalog
- Catalog admin bot - editing prices and stock from a barcode scanner via phone
- Integration with bank terminals (X-report reconciliation, alarm for discrepancies), scales via RS-232, network receipt printers (1 printer for 2 cash registers)

Separately: I also set up cash registers at points myself. PC, receipt printer, scanner, scales, terminal of any bank (Privat, Oschad, PUMB, Universal) - I will connect and configure. So I can handle both software and hardware turnkey.

All of this is currently working in a live retail network: 26 cash registers, 33.76 million UAH turnover, 29,631 receipts. No critical failures during this time.

My stack is Python (FastAPI, MySQL, SQLite, Tkinter) and JavaScript/React. If you don't have Python - I will be honest and we can discuss how to get into the project.

In two months, I will be able to do what you need. Give me a chance.

26 cash registers is not everything I manage with my software, and everyone is satisfied. There are still many cash registers that have not been updated. But as a system administrator, I am available 24/7 for all these cash registers.

My boss is so satisfied with me that he has no objections to me taking something at the level of your project.

If you're interested - write to me, I will show you live: the cash register, the dashboard, a real receipt in the tax office. One call for 30 minutes - and you will see everything for yourself.

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I have a good understanding of the logic behind POS systems, webhook-driven architecture, and integrations through API/SDK. In similar projects, the main challenge lies not only in sending receipts to the tax authority but in building a reliable middleware layer between the POS system and the fiscal core: handling queues, retry mechanisms, offline codes, receipt status control, synchronization of cashiers/cash registers, working with digital signatures, and stable error handling. These aspects determine whether the system will operate reliably under load in real business environments.

I have practical experience with Laravel, TypeScript, API integrations, event-driven systems, and complex backend logic. I have a good understanding of the specifics of state synchronization between the frontend POS terminal and backend services. I also pay great attention to fault-tolerant architecture: reconnect logic, queue processing, logging, error control, and stable operation in offline/online modes. For such systems, it is especially important to build a scalable architecture correctly from the start so that functionality can be expanded in the future without rewriting the core.

Work plan:

1. Analyze the API, SDK, and webhook architecture of the POS system.
2. Design the architecture of the PRRO application.
3. Implement the backend in Laravel.
… 4. Develop the UI for working with digital signatures and cash registers.
5. Integrate with the tax authority and the fiscalization mechanism.
6. Implement offline/online modes.
7. Handle offline codes and receipt queues.
8. Implement the logic for opening/closing the cash register.
9. Synchronize cashiers and POS entities.
10. Develop the frontend application for the POS terminal.
11. Integrate SDK events/actions.
12. Conduct load testing and fault tolerance.
13. Logging, retry logic, and error monitoring.
14. Deployment and final testing.

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