Some higher rate tax payers may have been issued a notice to complete a self-assessment tax return by HMRC. In this event the employee may be able to claim employment expenses and offset these expenses against taxable income. The net result may lead to an overpayment. The reason is quite simple;

A tax code will have been issued based on the estimated income in the following tax year. Each week or month tax will have been deducted and the tax code will show the amount the tax payer may earn before paying any tax.Therefore the initial tax coding issued could be incorrect as it does not take into consideration employment expenses.