Washington DC Complex Trust - Tax Due Payment Returned

Washington DC returned a tax due payment for a Complex Trust and provided no insight as to why. Is there an income threshold or another reason that a trust would not need to make a payment?  I followed the instructions in the book (TurboTax does not have software for trusts for Washington DC, so it has to be done by hand); there are income and tax brackets, but no exceptions are listed.  I looked on the Washington DC department of revenue website, this forum and on the internet and could not find any information  Thank you in advance.