He has said it is "a tradition in the commonwealth" for tax collectors to keep such fees.
Smolens called on Merriman to abide by the Commonwealth Court ruling and return the fees he has collected since 1989.
She estimated the total at $175,000.
Merriman already has anted up more than $46,000 from his personal bank account to make up a shortage in 1991-92 tax collections.
The Republican candidate for tax collector, William Ehart, has said he would keep the fees despite the court ruling.
"The 1989 township ordinance setting Merriman's compensation as treasurer did not give him the right to keep tax certification fees for himself," Smolens said.
"After setting a salary of $20,000, the township ordinance clearly states that the 'treasurer shall receive no other compensation of any kind for the collection or receipt of township moneys or for the performance of the duties of his office.' "
The tax collector, also known as the treasurer, receives an additional $12,000 yearly from the school district.
The fees usually range about $20 to $25, Smolens said, "but with the election coming up, they have been reduced drastically."
Merriman has never publicly listed the amount of fees collected.
Smolens has pledged that if she were elected, she would accept no salary and work for an amendment to the Home Rule Charter to abolish the tax collector's office and have taxes paid at a local bank.