Virtually all CDS are fully collateralized with daily cash settlement of variation margin. We show how the interest rate that the variation margin earns (the margin interest rate) affects the value of the CDS. Specifically, the authors show that all CDS can be valued as the expected net present value of the premium and default contingent payments using the same probability measure but different discounting rates determined by the margin interest rates on the individual CDS. For example, if the margin interest rate is fed funds then the discounting should be done on the OIS curve, and if there is no margin interest then there should be no discounting. The authors also show that this valuation approach should be used for both calibration and pricing to avoid any arbitrage opportunities between CDS with different margin interest rates.