Charities across Northern Ireland have been told their registration is considered "void" following a court ruling on how some decisions were made by their regulator.
The Charity Commission for Northern Ireland said those registered prior to May 2019 are likely to be affected.
Their status in law as charities is not altered by them temporarily not being on the formal register, the watchdog said.
It follows a court ruling earlier this year which found the commission cannot delegate decision-making powers to staff acting alone.
A judge described the case as having vital importance for the public at large.
In an online update on the implications of this ruling, the commission said: "If your charity was registered prior to May 2019, it is likely that the decision was made by a member of staff and not a panel of commissioners and is therefore considered to be void at this time."
Seamus McAleavey, chief executive of Nicva, an umbrella body for the voluntary and community sector in the north, said the issue will "cause a lot of confusion".
He said he would be seeking clarity from the Stormont's Department for the Communities (DfC).
"Certainly we need assurance. We need to make sure that whatever the actual problem is, whatever the flaw is, that needs to be fixed," he told BBC Radio Ulster's Nolan Show.
The watchdog said affected charities do not need to take any action, and can continue to operate as normal.
It said it is working with DfC to "seek a permanent resolution to the issue as soon as possible".
The commission is also contacting charity funders and support bodies to give clarification and request that it be taken into consideration when assessing applications from charities.
It added: "The fact that you are a charity in law is not altered by your temporarily not being a registered charity."
