The first that comes to mind is GNUCash, but I also asked chatgpt and here is what I got: There are several open-source accounting software options that work offline and support invoicing. Here are some popular ones: 1. **GnuCash** - Platforms: Windows, macOS, Linux - Features: GnuCash provides double-entry bookkeeping, stock/bond/mutual fund accounts, small-business accounting, reports, graphs, QIF/OFX/HBCI import, transaction matching, scheduled transactions, and more. It also allows you to manage invoicing and vendor management. - Website: [www.gnucash.org/](https://www.gnucash.org/) 2. **Manager** - Platforms: Windows, macOS, Linux - Features: Manager provides a wide range of accounting tools including invoicing, cash management, and financial reporting. While it has a cloud version, you can also download a desktop version that works offline. - Website: [www.manager.io/](https://www.manager.io/) 3. **FrontAccounting** - Platforms: Web-based (so you'd need a local server setup to run it offline) - Features: FrontAccounting is more than just accounting software; it's an ERP system. It can handle purchases, payments, inventory management, and sales. Invoicing is one of its core features. - Website: [frontaccounting.com/](https://frontaccounting.com/) 4. **KMyMoney** - Platforms: Windows, macOS, Linux - Features: Developed by KDE, KMyMoney is designed primarily for personal finance but can be adapted for small business use. It supports invoicing, investments, and various types of accounts. - Website: [kmymoney.org/](https://kmymoney.org/) 5. **TurboCASH** - Platforms: Windows - Features: TurboCASH is geared towards small to medium-sized businesses. It offers features like debtors, creditors, invoicing, stock, and more. - Website: [www.turbocash.net/](http://www.turbocash.net/) While evaluating which software to choose, always consider: - The complexity of your business operations and the features you need. - How user-friendly the software is. - Whether the software is actively maintained and updated. - The community and documentation/support available. It's always a good idea to test a few options before settling on one to see which one best fits your needs.