Offline Retail & Wholesale ERP -- 2

I need a full-featured ERP that runs entirely offline and can be used on a minimum of three workstations at the same time. Its main purpose is to handle both my retail and wholesale operations seamlessly, so the workflow has to accommodate walk-in POS sales as well as bulk, account-based orders.

Core modules I must see working together from day one are:

• Inventory management with real-time stock updates across all connected PCs
• Billing & invoicing that supports tax rules, discounts and returns
• A fast, cashier-friendly POS interface that pushes data straight into the inventory and invoicing engines

Even though the system is offline, I still need clean hooks that let me exchange data with my existing accounting software and our small CRM once a day through import/export or a lightweight sync tool.

Please build with stability, local database security and easy future scalability in mind. On delivery I will test the following acceptance criteria: stock counts syncing instantly between the three terminals while offline, invoices printing without delay, POS completing a sale in under five seconds, and exported files importing into my accounting package and CRM without manual edits.

Provide the full source, installation guide and a brief user manual so my team can run with it immediately.