  Let $P$ be a non-torsion point on an elliptic curve defined over a number
field $K$ and consider the sequence $\{B_n\}_{n\in \mathbb{N}}$ of the
denominators of $x(nP)$. We prove that every term of the sequence of the $B_n$
has a primitive divisor for $n$ greater than an effectively computable constant
that we will explicitly compute. This constant will depend only on the model
defining the curve.
