The total donations you claim can’t be more than your taxable income for the year.
If you need to file an IR3 income tax return, Inland Revenue will need your return to check your taxable income before they can process your claim.
If you have losses brought forward greater than your taxable income, you have no taxable income, so the credit cannot be claimed.
To avoid delays file your claim at the same time as you file your IR3.
Inland Revenue cannot process your claim before the end of the income year which it relates to. The exceptions are if you are completing the claim on behalf of a deceased person, or going overseas permanently or for a significant period of time.