using System.Text.RegularExpressions;
public static void Main()
string pattern = @"(?<=^\s\S{10})-(?=.*$)";
string substitution = @" ";
string input = @" K120613763-01 1100625 TL -11,008 0 -11,008
N123203270-02 1101024 PWL -387 0 -387
I200543078-01 1101029 PDDW -311 0 -311
A122285277-03 1101101 PWL 530 0 530
A127477426-03 1101101 PWL 458 0 458 ";
RegexOptions options = RegexOptions.Multiline | RegexOptions.IgnoreCase;
Regex regex = new Regex(pattern, options);
string result = regex.Replace(input, substitution);
Console.WriteLine(result);