A list of common Gift Aid errors has been published to help charities process claims more easily, amid concerns they could be claiming less than they are entitled to.
It was felt some Gift Aid claims were being delayed or rejected because of simple errors.
The most common errors include missing off donation dates and claiming the wrong amount because the claimant does not understand how the system works.
The list is an updated version of one published by HMRC in 2016.
HMRC has also devised a list of the most frequent questions on Gift Aid asked of its charities helpline, with the answers to each one included.
The questions include how to register and the time limits for making a claim.
It has also provided information on data that can be used when processing Gift Aid claims.
A CTG spokesman said: "We found that a good number of charities were not claiming as much as they were entitled to because the guidance was unclear or common misconceptions prevailed, including what was a valid address, or whether Gift Aid on sponsorship forms were valid if there was the same handwriting or ditto marks.
"This has been a good example of charities in our Gift Aid working group sharing best practice."