Looking to build or buy a SaaS Invoice Software

I am in need of a SaaS invoice software that is web-based and has payment integration, recurring payment and expense tracking capabilities. I am open to suggestions for existing software options that meet my needs. The ideal candidate will have experience in SaaS development and be able to provide a solution that is user-friendly and efficient. Key features required for the project include:

- Payment integration
- Recurring payments
- Expense Tracking
- Estimate/Quote Generation
- Web-based platform
- User-friendly interface
- Secure data storage and transfer

If you have experience in this area and can provide a solution that meets my needs, please get in touch.

The ideal solution will be competing with the following:

Zoho Books
Freshbooks
Wave Accounting
Odoo
HoneyBooks