Missing \begin{document}

What this error means

LaTeX found content (text, commands, or environments) before the \begin{document} marker. Everything before \begin{document} is the preamble — it should only contain class declarations, package loading, and global settings.

Common causes

• Accidentally placed text or content in the preamble
• The \begin{document} line was deleted or commented out
• Typo in \begin{document}

Code examples

\documentclass{article}
\usepackage{amsmath}

This text is in the preamble!  % Error

\begin{document}
More content here.
\end{document}

\documentclass{article}
\usepackage{amsmath}

\begin{document}

This text is correct.
More content here.

\end{document}

Related errors