The Treasury has launched a scheme allowing self-assessment taxpayers to donate any rebate due to them to charity.
Organisations must get onto an approved list at the Inland Revenue to be able to benefit from the scheme.
Donations will be transferred directly to the participating charities, and can be made through gift aid . For the first time anonymous donations will qualify for gift aid.
Around £3 billion was rebated to 3 million self-assessment taxpayers last year.
Helen Donoghue, administrator of the Charities Tax Reform Group, said: "It is an excellent initiative. We don't necessarily see this generating huge additional revenues to charities directly, but we do believe that it will encourage new donors."
The Inland Revenue is advising charities to encourage their own donors to take advantage of the scheme. To qualify, call the Inland Revenue on 0845 3020203 by 30 September.