under the tax rules it is a grantor trust (because you are the grantor and control the trust assets and are currently the beneficiary). about the only purpose the trust serves is to designate who inherits the property when you die. a grantor trust is a disregarded entity. if it has its own EIN then the tax laws require it to file a grantor trust return every year. you as the grantor/beneficiary then report all the income and expenses on schedule E of your 1040 as if the trust did not exist. if it doesn't have its own EIN then no tax filing is required for it and you report the same way on your 1040 - schedule E as if it does not exist. single-member LLCs are also disregarded entities. your tax person should have reported the rental on your return.
schedule C would only be appropriate if you rendered significant personal services to the renters like a B&B
if you filed without reporting the income, you now need to file an amended return. if you paid to have it prepared, the tax person should amend it for free and also be responsible for any penalties and interest.
and if a trust return was required the tax person should also pay any penalties for the late filing.
