Mind blown! We went out to dinner tonight and our bill was $37.09 so I did the math for 20% which came out to $7.41 but after I signed the bill I noticed the suggested gratuity said 20% was $6.93. I know my math wasn't wrong so I double and tripple checked it and I was right. 20% of $37.09 is $7.41 so I could not figure out how they were getting $6.93 THEN I realized... They were getting 20% from the PRE TAX amount! I had no idea!!! I thought you tipped off the BALANCE DUE not the subtotal before taxes. Wow!! Crazy! Did you know that??