D.C. Mun. Regs. tit. 9, r. 9-329
As prescribed by Section 370, the information required to be accurately completed on the mixed use form must be electronically submitted to the Deputy Chief Financial Officer not later than September 1st of the year in which the forms are mailed or made electronically available on the OTR online portal, in the discretion of the Deputy Chief Financial Officer, to affected taxpayers.
Mixed use forms will be mailed or made electronically available on the OTR online portal, in the discretion of the Deputy Chief Financial Officer, to affected taxpayers approximately thirty (30) days prior to the due date provided for in § 329.1.
In computing any period of time prescribed or allowed, the day of the act from which the designated period of time begins to run shall not be included. The last day of the period so computed shall be included, unless it is a Saturday, Sunday or a legal holiday, in which case the period shall run until the end of the next day which is not a Saturday, Sunday, or legal holiday.
An extension of time to submit the forms may be granted, in the discretion of the Deputy Chief Financial Officer, for good cause.
A request for an extension of time to file shall be submitted electronically to the Deputy Chief Financial Officer not later than August 20th of the year in which the forms are mailed or made available electronically, in the discretion of the Deputy Chief Financial Officer, to affected taxpayers. Requests for extensions delivered after that date will not be granted.
If, in the opinion of the Deputy Chief Financial Officer, a mixed use form submitted prior to the deadline set forth in this section has not been accurately completed (that is, it is either inaccurate or incomplete), the Deputy Chief Financial Officer may so inform the affected taxpayer (or the taxpayer's agent), and request that the form be accurately completed. In no instance shall the Deputy Chief Financial Officer be accountable for the accuracy or correctness of the mixed-use form supplied and certified to by the affected taxpayer or agent of the taxpayer.
The mixed-use form shall be filed annually on or before the date provided for in § 329.1, as prescribed in Section 370.
Failure of the Deputy Chief Financial Officer to mail or make available electronically, in the discretion of the Deputy Chief Financial Officer, a mixed use form to an affected taxpayer shall in no manner diminish the obligation of the taxpayer to secure and file in a timely manner a mixed use form.
D.C. Mun. Regs. tit. 9, r. 9-329