<p>Mastering the relationship between different numerical formats (i.e., digits, number words, and non-symbolic quantities) is an important foundational skill for later math competencies. However, the neurocognitive mechanisms of this relationship remain poorly understood in children. Consequently, the current study examines the integration between digits, number words, and dots in a sample of 34 primary school children (aged 7 to 14 years) with an electroencephalography paradigm tagging the frequency of stimulus presentation. In an oddball paradigm, we presented children with mixed notation sequences (i.e., dots – words, digits – dots, words – digits) at a rate of 166 ms per stimulus while manipulating the magnitude of the deviant numbers in an experimental (rule = standards &lt; 5, deviants &gt; 5) and control conditions (no rule). We observed deviant responses in the experimental but not in the control condition, with the strongest responses for dots – words, followed by words – digits and finally, digits – dots. These findings suggest that, in children, numerical magnitude information is automatically extracted irrespective of the format at least under implicit and rapid presentation conditions.</p>