documentclass[a4paper]{scrlttr2}
usepackage[top=2cm, bottom=1cm, left=2cm, right=2cm]{geometry}
usepackage{graphicx}
usepackage{lmodern}
usepackage[utf8]{inputenc}
usepackage[T1]{fontenc}
usepackage[ngerman]{babel}
usepackage{color}
usepackage[hidelinks]{hyperref}


usepackage[german,comma]{invoice}
begin{document}
begin{letter}
begin{invoice}{Euro}{0}
ProjectTitle{IT Random Consulting} %
Fee{Task 1}{10}{1}
end{invoice}
end{letter}
end{document}