Warning: if the taxman gets your bill wrong it's officially your fault

More than 20 million codes, which tell you how much of your income will be tax-free, are sent to 16 million people at this time of year. But already The Daily Mail has seen several cases where the code - a combination of letters and numbers - is wrong. Mistakes typically occur when someone has several sources of income or where they have received a large one-off boost, such as a dividend payment, in the previous year. This can leave someone paying too much or too little tax in future years. The problem is compounded because a rule that allows taxpayers to fight unfair bills is bein...