This work is my adaptation of the original dapper-invoice class to which almost all credits are to be given.
A showcase of this template ca be seen in the example directory.
Here is the default code one should write when using yInvoice:
\documentclass{yInvoice}
\business{<Your (business) name>}
\invoiceNumber{<invoice number>}
\client{<client name>}{<client adress line 1>}{<client adress line 2>}[<client adress line 3>]
\project{<project name>}
\contact{<contact name>}[<contact phone number>][<contact mail>]
\yourself{<your name>}{<your adress line 1>}{<your adress line 2>}[<your adress line 3>][<your phone number>][<your email>]
\bank{<bank name>}{<your iban>}
\duein{<invoice due in # days>}
\balancePrice{<balance price>}
\begin{document}
\printInvoiceHeader
\begin{costsDescription}{<total price including already paid>}{<already paid>}
\costEntry{<Entry name>}{<date>}{<entry description>}{<hours number>}{<price per hour>}{<total cost>}
\end{costsDescription}
\vfill
\textit{<Your name>}
\end{document}