Why do lease ads say 'plus tax' and 'due at signing'?

Lease ads usually highlight a low monthly payment, and the fine print reveals what it assumes: a specific amount due at signing, a particular term and mileage allowance, a trim level, excellent credit and taxes not included. A lower payment can simply mean more cash upfront. To compare fairly, ask for the full terms in writing and calculate the total cost of the lease, including everything paid at signing.