This is the amount of premium on which the full commission is paid. This field is especially important if you are using the optional commission module because a percentage of commission is applied to it for calculating commissions.
When the premium mode is other than annual, the full modal premium will often be applied 100% to the base premium until the full base premium is paid. Only then will the premiums be applied to the excess premium.
Example
Assume the annual premium is $1,200 and the monthly premium is $100. Also assume the annual base premium is $600 and the annual excess premium is $600. The monthly premiums of $100 will often be applied to the base premium of $600 and only after $600 is paid will the premiums be credited to the excess premium account.