I was reading in a dining review post that when the person was going to pay the tip in cash they were informed by a few of the servers at different restaurants that they needed to indicate how much they were going to tip by writing the amount on the bill before they paid. I understand that the bill (DDP) will arrive with a suggested amount of either 18 or 20% which is fine. I do plan on tipping in cash however. So what is the logic behind them having you write the tip down before you leave the table. Also is this the normal procedure for most table service places?