I own my mobile home and pay lot rent in SC. I also use a room in my home for business. Can I write off the lot rent in State or Federal return?

[smlehoullier]

If I can, it is a percentage based on the size of the room used for business?

[DanielV01]

It depends.  If you claim the Home Business Office Deduction (Form 8829), your lot rent can be included as one of the expenses that gets prorated based on the percentage of square footage of the area you use for business.  However, if you use the safe harbor calculation instead, you are not going to get any deduction for the lot rental.  South Carolina's tax calculations begin with Federal taxable income.  This means that if the deduction has reduced your income reported to the IRS, it has reduced your income for South Carolina already.  

Otherwise, South Carolina does not have a specific deduction for the lot rent.