The price of a bond is the present value of its future cash-flows. To avoid the impact of the next coupon payment on the price of a bond, this cash flow is excluded from the price of the bond and is called the accrued interest. In finance, the dirty price is the price of a bond including any interest that has accrued since issue of the most recent coupon payment. This is to be compared with the clean price, which is the price of a bond excluding the accrued interest.