Many charities could be entitled to refunds because they have been paying too much climate change levy, according to accountants Saffery Champness.
The levy was introduced in 2001 and is added to fuel bills, but charities were exempted. Even if there is an element of business use by a charity, it is still exempted as long as the business use is less than 40 per cent of total fuel usage.
But many charities are unaware of this exemption and could be paying too much tax, said partner John Turnbull-Kemp.
"The vast majority of charities are involved in some form of non-business activity but may have failed to measure their non-business use of fuel properly, leading to unnecessary payments.
"Those who find that the levy has been incorrectly paid may be able to claim it back retrospectively."
He added that many charities' operations include business activities, but they account for less than 40 per cent of their fuel bills.