Continuing with the previously mentioned example, if the cost of installing 8 solar panels is €5,800 and the ICIO fee at 4% indicates that approximately €232 needs to be paid, but the solar panel is in an area where the ICIO is rebated at 90%, it would be necessary to subtract 90% from the fee amount.
That is, first we calculate what 90% of €232 is by using a proportion, and with that result, which is €208.8, we perform a simple subtraction of that amount from the total. The resulting figure (€232 - €208.8 = €23.2) is the final amount that would need to be paid. In other words, €23 instead of €232.