Invoiceberry, Zoho Invoice and Invoicely are some of the invoicing tools that provide unlimited invoices under their free plan. However, Invoicely is the only invoicing tool which has unlimited invoices for unlimited clients. Other tools have limitations on the number of clients, you can send the unlimited invoices to. You can also check out Waveapp which is a complete free tool to send unlimited invoices. Using Waveapp you can send unlimited invoices in any currency and also accept credit cards and save its information for later use. It also offers automatic payment reminders and recurring invoices for repeat businesses.