In addition to the penalty imposed by section
7203 (relating to willful failure to file return, supply information, or pay tax), if any partnership required to file a return under section
6031 for any taxable year—
such partnership shall be liable for a penalty determined under subsection (b) for each month (or fraction thereof) during which such failure continues (but not to exceed 5 months), unless it is shown that such failure is due to reasonable cause.