The new online Gift Aid filing system will be introduced on 22 April, HM Revenue & Customs has announced.
The new system, called Charities Online, will enable charities make repayment claims electronically.
New HMRC guidance, published today, includes details of the transitional arrangements, which say that HMRC will continue to accept the current paper forms until 30 September.
HMRC said the guidance would explain what Charities Online means for charities and how they can prepare for it.
The new system will require some changes to the information that must be submitted to HMRC. Charities will need to provide each donor’s address, in addition to their name, date of donation and the amount given.
A spokeswoman for the Charity Finance Group said: "It is really important there is a relatively lengthy transition period because there might be costs and it will take a lot of preparation.
"It might need to be extended a bit further in certain circumstances if a charity is not quite ready in time.
"It is important charities look at this information now and are aware of the changes. The transitional period is going to be relatively small. If there is going to be a cost associated with updating their databases, charities need to start planning for it now.
"There could also be cash flow issues in April if it takes time to bed in."