D.C. Mun. Regs. tit. 9, r. 9-151
If any person fails to make and file a return within the time prescribed by law, (except in the case of an employer filing quarterly returns), unless it is shown that the failure is due to reasonable cause and not due to willful neglect, there shall be added to the amount required to be shown as the tax on that return five percent (5%) of the amount of the tax (if the failure is for not more than one (1) month), with an additional five percent (5%) for each additional month or fraction of a month during which the failure continues, not exceeding twenty-five percent (25%) in the aggregate.
For purposes of this section the amount of tax required to be shown on the return shall be reduced by the amount of any part of the tax which is paid on or before the date prescribed for payment of the tax and by the amount of any credit against the tax which may be claimed upon the return.
With respect to declarations of estimated tax, for the purposes of this section, the amount and due date of each installment shall be the same as if a declaration had been filed within the time prescribed showing an estimated tax equal to the correct tax reduced by the amount of credit for tax withheld.
In the case of any employer who is required to withhold taxes on wages, make a return of those taxes, and pay to the District the taxes required to be withheld, and who fails to withhold the taxes, make the return, or pay to the District the taxes required to be withheld, there shall be imposed on that employer a civil penalty (in addition to any criminal penalty provided by law) of five percent (5%) of the amount required to be shown as tax on the return if the failure is for not more than one (1) month, with an additional five percent (5%) for each additional month or fraction of a month during which the failure continues, not exceeding twenty-five percent (25%) in the aggregate.
If any corporation, financial institution, or unincorporated business fails to pay the amount of franchise tax within the time prescribed by law or by the Mayor or Council in pursuance of law, five percent (5%) of the tax shall be added to the tax for each month or fraction of a month that the failure continues, not to exceed twenty-five percent (25%) in the aggregate.
The penalty for failure to pay the franchise tax within the time prescribed shall be, in addition to all other penalties, prescribed by the Act.
D.C. Mun. Regs. tit. 9, r. 9-151