Ive seen other examples and tried - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string I am not sure what I am doing wrong, I just started coding my first Iphone App This is what I am trying to do I have 4 textfields and each has a limit on number of letters while typing I have done this using the below code - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string { int valid; NSString *cs2 = [textField.text stringByReplacingCharactersInRange:range withString:string]; // int charCount = [cs2 length]; if(textField == cvv){ valid = 4; }else if(textField == cardName) { valid=26; }else if(textField == expDate) { valid=5; // if (charCount == 2 ) { // textField.text = [cs2 stringByAppendingString:@"/"]; // textField.text = cs2; // return YES; // } }else if(textField == acNumber) { valid=19; } return !([cs2 length] > valid); Works fine till here, I have a textfield where the user enters Exp date and would like to format it as if I am entering 112 then it should display as 01/12 and if I enter 2 then it should display as 1122 I tried checking if the length of the textfield value is 2 then append a / but then that gives me when I enter 12 it gives 11/22