This error will appear when the alignment character & is used inappropriately. This alignment character & is used for aligning elements in specific environments, such as table, align, matrix etc.
Common Causes of Error
Not writing \&
Whenever you want to use the ampersand sign & as a part of text while writing, like in a title, you need to write it as \&. If you do not do so, you will get the following error message.
The name of the movie is 'Kapoor & Sons'
Misplaced alignment tab character & document.tex, line 6
l.5 The company is named 'Kapoor & Sons' I can't figure out why you would want to use a tab
mark here. If you just want an ampersand, the remedy is simple: Just type `I\&' now. But if
some right brace up above has ended a previous alignment prematurely, you're probably due for more
error messages, and you might try typing `S' now just to see what is salvageable. [1
To avoid this error, please change & to \&.
Matrix macro used instead of amsmath:matrix
The macro matrix is often used incorrectly. Because in actual we want to use the environment matrix provided by the amsmath package. In case you forget to load the amsmath package and write the code as below, an error message misplaced alignment tab will appear on the screen.
$$
\begin{matrix}
7 & 5 & 1 \\
8 & 0 & 2 \\
9 & 5 & 3
\end{matrix}
$$
The error occurred because of the incorrect usage of the matrix macro. To solve this issue, include the amsmath package.
% In the preamble (before \begin{document} that is, beginning of document)
\usepackage{amsmath}
% Now, in the document
$$
\begin{matrix}
7 & 5 & 1 \\
8 & 0 & 2 \\
9 & 5 & 3
\end{matrix}
$$