Your company will need to book the total value of the share options as an accounting expense. The value of share option depends on 6 main factors, two of which may be affected by the US credit downgrade. In principle, the credit downgrade will have negative impact on a company’s stock price, as the discount rate rose. It lowers the option value. The second factor is the risk free rate. A higher risk free rate will give rise to higher option value. US risk free rate may rise. But if your company is based in HK, and if HK risk free rate is not affected, the option value does not change due to an unchanged risk free rate. In sum, the downgrade of US credit rating may bring you a lower accounting cost of issuing new share options. Hope that helps.