Add additional parameter to syntax: [ ; Logical calc_method = TRUE() ] In semantics add additional parameter: "calc_method A logical value that specifies how to treat the case where settlement>first" Then, under semantics add the following new paragraph: "If calc_method is TRUE (the default) then ACCRINT returns the sum of the accrued interest in each coupon period from issue date until settlement date. If calc_method is FALSE then ACCRINT returns the sum of the accrued interest in each coupon period from first date until settlement date. For each coupon period, the interest is par*coupon*YEARFRAC(start-of-period;end-of-period; basis)"