\documentclass[12pt]{isodoc}
\usepackage{isowybo}
\setupdocument{
ourref=8234,
date=20060401,
subject=Declaratie verzending aanmaningen,
to=NTG\\Maasstraat 2\\5836 BB Sambeek
}
\begin{document}
\invoice{%
\itable{
\iitem{enveloppen}{6,60}
\iitem{postzegels}{9,00}
\itotal{15,60}
}
\\[3ex]\accountdata
}
\end{document}