Permanent endowment
Some charity funds cannot be spent at all. Permanent endowment is capital the charity is required to retain, typically because the donor said so.
The trustees may normally use the income but not the capital. The Charities Act 2022 introduced new statutory powers allowing release or borrowing against permanent endowment in defined circumstances, with thresholds and conditions.
Check whether a fund is genuinely permanent endowment before treating it as unspendable — or as spendable. See releasing permanent endowment and restricted funds, which is a different thing.