I made a mini page like below. It compiled without any error, however, I am getting following message in log:

Underfull \hbox (badness 10000) in paragraph at lines 104--109


I am trying to fix above message.

\begin{minipage}[b]{0.4\linewidth}
\dotfill\\
Prof. XYZ\\
Department of XYZ\\
University of whatever, \\
City, Country\\

Date: ............\\
\end{minipage}


Remove \\ from the last two lines:

  \begin{minipage}[b]{0.4\linewidth}
\dotfill\\
Prof. XYZ\\
Department of XYZ\\
University of whatever, \\
City, Country              %<--- here

Date: ............         %<----and here
\end{minipage}


Bad boxes should go away. Forcing a line break followed by a blank line{which amounts to a paragraph break) and a line break after the last line are responsible for the bad boxes.

• there are literally hundreds of messages answering this question. one that has been cited before is Implicit newline at the end of each paragraph?. it would be a good thing to have a "stock" question that can be cited as a duplicate, that would explain many situations. – barbara beeton Sep 5 '14 at 13:26