CharityCheckout has reduced its 5 per cent platform fees for charities and will offer donors the chance to cover costs.
Under the new model, charities will have the option to pay a 5 per cent platform fee on donations they receive, but the default amount will be zero.
CharityCheckout donors will also have the option of adding tips, for example in the form of 5 per cent on top of any donation.
A processing fee will still apply, which is 0.5 per cent plus 20 pence.
Charities will receive an extra £1 for every £20 that is donated under the new model, a CharityCheckout spokeswoman said.
The move comes after Virgin Money Giving and JustGiving dropped their platform fees earlier this year.
CharityCheckout said the change to its model came after a survey with 1,448 charity clients about what fee model they would prefer.
Chester Mojay-Sinclare, founder and chief executive of CharityCheckout, said: "Donors will now be given the option to leave voluntary tips to cover the donation service. These funds will enable us to continuously improve and innovate, ensuring that donors enjoy a positive giving experience and our charities see the benefit of superior fundraising technology."