Working with HM Revenue & Customs (HMRC) and 15 charities, BDO Stoy Hayward's tax investigations team has put together the guidelines to clear up the confusion over claims for Gift Aid.
The move is in response to HMRC's concerns about incorrect Gift Aid relief claims for fundraising dinner events, and its in-vestigation into a number of charities.
The guidelines stipulate that for Gift Aid to apply, a donation must be purely voluntary.
Where a charity specifies a "minimum donation" or a fixed price on a ticket for an event, such donations would not be regarded as voluntary so Gift Aid would not apply.
Instead, charities wishing to claim the tax benefit should make it clear they want voluntary donations by specifying a "suggested voluntary donation of pounds X".
By doing this, the charities are effectively staging free events for potential supporters, and any money paid can be considered as donations, which qualify for Gift Aid.
Daniel Dover, head of the tax investigations group at BDO Stoy Hayward, said this could pose a problem for charities in that when donations are requested on this basis, the charity cannot rely on a minimum level of proceeds from the event.
He added: "A careful judgement must be made as to whether the level of voluntary donations will be sufficiently generous to cover the cost of organising the event and provide additional funds to make the event worthwhile."
The guidelines also state that benefits such as the dinner must not be received by donors in return for their voluntary donations or the cash might not qualify for Gift Aid.
Dover said the charities involved in drawing up the guidance declined to be named because they might have not have made the most of the Gift Aid regulations in these circumstances.
Penny Rae, head of operations at Cancer Research UK, which holds fundraising dinners, said: "Gift Aid is complex and any additional advice is welcome."
But she added that the guidelines were unlikely to change the way CRUK works because fixed ticket prices ensure that costs will be met.