Tab is not functioning in PuTTY?

run below command on terminal. 

sudo vi /etc/bash.bashrc

copy below script and paste and save it.

# enable bash completion in interactive shells

if ! shopt -oq posix; then

  if [ -f /usr/share/bash-completion/bash_completion ]; then

    . /usr/share/bash-completion/bash_completion

  elif [ -f /etc/bash_completion ]; then

    . /etc/bash_completion

  fi

fi