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# LaTeX Error: Missing \begin document

This error appears when you have forgotten to include **`\begin{document}`** in your document. It can also appear if you have not written **`\documentclass[...]{...}`** at the beginning of your main document.

## Common Causes

**Forgetting to include \begin{document}:**

The most basic cause of this error occurs when you have forgotten to write **`\begin{document}`** after the preamble in your main document. If you make this mistake, you will generate the error message shown below:

main.tex, line 5

LaTeX Error: Missing \begin{document}.

See the LaTeX manual or LaTeX Companion for explanation. Type H for immediate help. ... You're in trouble here. Try typing to proceed. If that doesn't work, type X to quit.

To resolve this error, simply make sure that you have included **`\begin{document}`** after the preamble in your main document. See [here](/latex/latex-basics/01-learn-latex-in-30-minutes.md) to learn more about how to structure documents in LaTeX.

**\documentclass\[...]{...} in wrong place:**

Another common cause of this error is if **`\documentclass[...]{...}`** is written in the wrong place. This must be written at the start of the main document. If you have a separate file for your preamble, you **cannot** include **`\documentclass[...]{...}`** in that file. It still must appear at the top of the main project file, or else only the preamble file will be compiled.

**Main document set incorrectly:**

This error may also appear if you have set the main document incorrectly in the left hand menu. This can happen if **`\documentclass[...]{...}`** is written in the wrong place, so you should correct this first if needed. To change the choice of main document, open the left hand menu:

![Lefthandmenu.PNG](/files/N069lBukH6jO54osMq5e)

and go to the *Main document* drop down menu:

![Maindocument.PNG](/files/Ud4ZORFsRkn1MusL2cs5)


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