The smog certification fee — the cost of the actual smog inspection — is paid by the dealer for retail sales. This is your cost of doing business; you cannot pass the smog inspection fee to the buyer as a separate line item. The smog certificate is a requirement for the sale, and providing it is the dealer’s responsibility.
However, the DMV smog transfer fee — which is a state fee collected at the time of transfer — is a government-imposed fee that is collected from the buyer as part of the transfer costs. Don’t confuse the two: the smog inspection fee (what you pay the smog station) is your expense; the smog transfer fee (what DMV collects at transfer) is the buyer’s expense. The $25 smog abatement fee for vehicles in their 7th and 8th exemption years is also collected from the buyer as a transfer fee.