The ACDP had met with Independent Electoral Commission (IEC) officials who had referred the matter to the Electoral Court for advice, the ACDP said in a statement.
Should the court acknowledge the error and rule in favour of the ACDP, the party would gain a seventh seat in the Assembly.
Analysis of the election results on a district by district basis earlier this week by the ACDP revealed capturing errors in eight voting districts in Gauteng, the Eastern Cape and Cape Town.
The errors involved a mix-up of votes for the ACDP, the ANC, and Azapo, with Azapo's support significantly reduced.
"This significant decrease in the percentage of support gives Azapo only one seat in the National Assembly, according to formulas calculating how many seats each party qualifies for.
"Despite a loss of votes in the Gauteng and Eastern Cape districts, the ACDP qualifies for that seat," the ACDP said.
"In a meeting between the ACDP, IEC and Azapo in Pretoria on Thursday, Azapo representatives refused to give up the seat, claiming that the results had been declared final and could not be changed.
"IEC officials have now taken the matter to the Electoral Court for further advice," the ACDP said.