I am Giorgio, a senior software developer from Italy with more than 20 years of experience, specialized in desktop application development of every type, building it from scratch or using Microsoft Office suite (look at my portfolio for some application developed by me).
I have already developed several application for invoicing, you can see one of them in my portfolio for another customer: this is a green application, namely a software than doesn't need installation, so it can easily be stored and executed from a PC folder, an USB device or an online drive space as Google Drive, Microsoft One Drive or DropBox.
If you are interested or need more information, feel free to contact me on Freelancer's chat, because only the employer can do it.
Obviously if you prefer we can also speak in Italian.
Regards