template.tex.erb

\documentclass[a4paper,backaddress=true]{scrlttr2}
\usepackage[utf8x]{inputenc}
\usepackage{color,calc,ngerman,mathptmx}
\usepackage{eurosym}
\usepackage{booktabs}
\usepackage{graphicx}
\usepackage{geometry}
\usepackage{tabularx}

\renewcommand{\familydefault}{\sfdefault}

\date{<%= @date.strftime("%d. %B %Y") %>}
% DIN Ausrichtung am Adressfeld statt typographisch korrekte Einrückung
\makeatletter
\@setplength{refwidth}{\textwidth}
\@setplength{refhpos}{\useplength{toaddrhpos}}
\setlength{\oddsidemargin}{\useplength{toaddrhpos}-1in}
\makeatother

\setkomavar{subject}{Invoice No. <%= @invoice_number %>}
\setkomavar{fromname}{Your Name}
\setkomavar{fromaddress}{Street 123\\12345 Megatown\\Deutschland}
\setkomavar{fromphone}{+49 (0)1234 555 666 77 }
\newcommand\fromwebsite{https://example.de} % is not a KOMA var

\setkomavar{frombank}{Target Bank\\
    IBAN: DE24 11111111 2222222222\\
    BIC: ABCDEF44}
\setkomavar{fromemail}{you@email.de}
\setkomavar{signature}{\usekomavar{fromname}}
\newcommand\ustid{USt-ID: DE123456789}
\setkomavar{place}{Megatown}

\firsthead{\null\hfill
   \parbox[t][\headheight][t]{5cm}{%
       \raggedright
       \color[gray]{.5}%
       \usekomavar{fromname}\\
       \usekomavar{fromaddress}\\[\baselineskip]
       \ustid
   }%
}

\firstfoot{%
    \scriptsize{%
        \parbox{\useplength{firstfootwidth}
    }{%
        \rule{170mm}{0.3pt}
        \color[gray]{.5}%
        \begin{tabularx}{\textwidth}{X X X}
            \begin{tabular}{ll}
                \usekomavar{fromname}\\
                \usekomavar{fromaddress}\\
            \end{tabular} &
            \begin{tabular}{cc}
                E-Mail: \usekomavar{fromemail}\\
                Tel: \usekomavar{fromphone}\\
                Web: \fromwebsite\\
            \end{tabular} &
            \begin{tabular}{rr}
                \usekomavar{frombank}\\
            \end{tabular}
        \end{tabularx}
    }}
}

\nextfoot{%
    \parbox{\useplength{firstfootwidth}}{
        \begin{tabular}{ll}
            \usekomavar{fromname}
        \end{tabular}\hfill
        \begin{tabular}{cc}
            \today
        \end{tabular}\hfill
        \begin{tabular}{rr}
            \thepage
        \end{tabular}
    }
}


%%
%% Document
%%

\begin{document}
\setlength{\parindent}{0pt}
\setlength{\parskip}{0.5\baselineskip}

\begin{letter}{Bright Market, LLC\\dba: FastSpring\\8 E. Figueroa St \#240\\Santa Barbara, CA 9310}
\opening{}

\vspace{2\parskip}

\begin{tabular}{rp{10cm}rr}
\toprule
Qty & Description & Price & Amount \\ \midrule
1   & Digital Goods, software and ebooks, \newline products sold by distributor, FastSpring & <%= @amount %> & <%= @amount %> \\
\bottomrule
\multicolumn{3}{r}{Subtotal:} & <%= @amount %> \\
\multicolumn{3}{r}{Tax:} & -- \\
\multicolumn{3}{r}{Total:} & <%= @amount %> \\
\end{tabular}

\vspace{2\parskip}

\closing{Thank you for your business}

\end{letter}
\end{document}