In a statement, the CTG said gathering data on the amount of VAT relief claimed would allow better evaluation of how changes to VAT or its reliefs could affect the sector.
This would put the charity sector in a better position to defend the reliefs it currently has, the CTG said.
"We must put ourselves in the position of being able to defend what we value about the VAT system and persuade government to consider changes where the system can be improved," a statement from the CTG said.
"The only effective way to do this is to have the statistical data to demonstrate the impact on a charity’s ability to perform its mission in the first instance and then the broader contribution made towards the socio-economic wellbeing of the country, including the creation of employment and taxes paid to the Treasury."
The survey is being run by the economics consultancy London Economics, which was commissioned by the CTG, and will focus on a "representative sample" of charities, the CTG said.
The survey follows on from the independent Charity Tax Commission’s final report, which was published earlier this year.
As well as calling for better data on the tax reliefs charities receive, the tax commission’s report also calls for a universal Gift Aid declaration database and mandatory payroll giving for all but the smallest employers.