Term for the amount from which commission is calculated

I'm looking for a word for the larger amount from which a salesman's commission might be calculated.

Something like sale price presupposes that his commission is calculated from that particular figure.

I have used principal before because it's a very similar concept to interest being calculated from the principal of a loan, but it's technically incorrect for this purpose.

I've considered dividend (i.e. dividend ÷ divisor = quotient) but this has other connotations

Whereas multiplicand (i.e. multiplicand × multiplier = product) is too obscure.

Anyone got a winner?

Consider base

a number that is multiplied by a rate or of which a percentage or fraction is calculated

Or possibly base amount.