There are two internationally important model agreements
for DTAs: one by the OECD, and another one by
the UN. The latter is more or less based on the OECD
model, but with some rules more favourable to developing
countries. Regarding intra-firm relations, the model
agreements both assume that a parent company and its
subsidiary are separate entities that should interact in
the same way as with third parties – i. e., based on the
Arm’s Length Principle.