New research could finally provide a reliable figure on annual levels of giving to charities.
The study aims to reveal not only how much is generated by the sector as a whole but also by different demographic groups. It will also identify trends in giving.
NCVO and Charities Aid Foundation (CAF) are collaborating on the research, which should be concluded by summer, when the first joint report is due to be published.
NCVO's head of research Karl Wilding said: "A good solid source of information on individual giving is invaluable for the sector's strategic planning.
"Charitable donations are not only important in financial terms, they are also a measure of the public's support of charities' activities.
"An understanding of the fluctuations in the public's support for good causes can, on the one hand, help charities to plan their future work and, on the other hand, inform policy changes such as the Chancellor's recent decision to extend payroll giving."
Attempts to find an accurate figure have so far proved elusive. NCVO's quarterly figures are based solely on an NOP survey that is thought to inflate real levels of giving because it is based on people's recollections.
Other methods, such as CAF's top 500 fundraising charities research, based on charities' accounts, are also suspect because many organisations do not isolate their annual income from individual, as opposed to general, voluntary income.
CAF and NCVO's research will be based on NOP opinion polls on individual giving as well as being informed by other sources of information, such as Inland Revenue figures on payroll giving and Gift Aid and the Family Expenditure Survey.
The programme will be supported by an independent advisory group comprising voluntary-sector fundraising experts and specialist academics. These include Andrew Watt, head of policy at the Institute of Fundraising, Meta Zimmeck, head of the Home Office Voluntary and Community Research Section, Margaret Shaw, head of marketing and management information at ActionAid, Chris Farmelo, head of quantitative analysis at the Future Foundation, and Roger Tarling, of the Institute of Social Research, Surrey University.
Members of the group will be able to submit other sources of data to the research.
"We are aiming at a complete authoritative figure on the annual level of giving and trends in giving," said CAF's director of research Cathy Pharoah.
"We will be triangulating from different sources. We also want to identify trends in giving - whether and where it is going up or down, for example in different income groups," she said.
Pharoah added that one of the purposes of the new research programme was to explain discrepancies between different forms of research on giving.
"If, for example, the Top 500 fundraising survey says that giving is down, and the NOP survey says that it isn't, we will try and find out why," she said. "We will be looking to create a single story that is the best estimate."