What if a political organization fails to pay the tax shown on Form 1120-POL?

A political organization that fails to timely pay the tax shown or required to be shown on Form 1120-POL, must pay an additional amount equal to 0.5 percent of the unpaid tax for each month (or partial month) the tax is not paid up to a maximum of 25 percent of the unpaid tax, unless the organization shows that the failure was due to reasonable cause.