There appears to be a grey area regarding the handling of late payment fees (or a difference of opinion by other tax preparers). While I would normally consider the fees tax deductible, the enormity of the fees for this business causes me to hesitate. Taxpayer stopped paying on credit card for a period of time, thus the large fees The credit card company does not show the late fees as interest when they provide the year-to-date interest paid. Another tax preparer noted Bailey TC Memo 1991-385 and after reading the ruling, I was leaning toward non-deductible, but do not want to omit a deduction at the taxpayer's expense if actually valid .