Before or After tax discount rate

We always use the after tax cost of debt when calculating the cost of capital. The article converts the real cost to the money/nominal cost and since the real cost must already be after tax then the nominal cost will automatically be after tax. Tax is only ignored when calculating the return to investors, because investors are not affected by company tax. I do suggest that you watch my free lectures on this. The lectures are a complete free course for Paper FM and cover everything needed to be able to pass the exam well.

Yes, you would then assume it was already after tax.