As is true with other forms of over-the-counter derivatives, CDS might involve liquidity risk. If one or both parties to a CDS contract must post collateral (which is common), there can be margin calls requiring the posting of additional collateral. The required collateral is agreed on by the parties when the CDS is first issued. This margin amount may vary over the life of the CDS contract, if the market price of the CDS contract changes, or the credit rating of one of the parties changes. Many CDS contracts even require payment of an upfront fee (composed of "reset to par" and an "initial coupon.").