Magazines often have more than one rate card. In many cases they have two: a rate card with net rates and a rate card with gross rates. Net rates are usually given to advertisers who place their ads directly with the magazine (retail or regional advertisers). Gross rates are given to advertisers whose ads are placed by an accredited advertising agency (national advertisers). This is because advertising agencies get a 15% commission on ads placed in magazines. If you don't gross up your net rate, that 15% commission will come out of your profit when an agency places an ad.