New one for me.  DC resident renting out 3/4 of home.  This is reported on both 1040 and D-4O DC tax return.  I've done D-30 unincorp business returns for MD residents but not for DC residents.  If taxpayer has to pay D-30 unincorp business tax to DC and also pay on their resident D-40 isn't this a duplication of tax?  Yes, revenue is above $12,000 so not exempt.