Every registered charity files accounts. Before a large gift, look it up: Australia, Australian Charities and Not-for-profits Commission (ACNC) Charity Register acnc.gov.au/charity/charities (search by name or Australian Business Number; shows deductible gift recipient (DGR) status and financial reports); UK, Charity Commission via gov.uk/find-charity-information US, Charity Navigator charitynavigator.org/ (profiles at /ein/ followed by the Employer Identification Number) and Candid guidestar.org/search Canada, Charity Intelligence charityintelligence.ca/charity-profiles/a-z-charity-listing ProPublica's Nonprofit Explorer shows raw US filings.
What to look for: is it registered at all; is the donation tax-deductible where you live (DGR in Australia, Gift Aid in the UK, 501(c)(3) in the US); what share of spending goes to programmes; and does the annual report say what changed, not just what was collected. Note that some ACNC and Charity Commission pages block automated tools but open normally in a browser.
Companies and community interest companies (CICs) (Plastic Bank, Common Seas, Planet Patrol) can still do good work, but a gift to them is not a charitable donation.