You can easily check a number of things online: 1) incorporation using the Secretary of State business lookup tool for the organization’s HQ state. 2) exempt status with the IRS: https://www.irs.gov/charities-non-profits/search-for-tax-exempt-organizations. 3) financials through https://projects.propublica.org/nonprofits/. 4) “transparency” rating through https://candid.org/ 5) BBB complaints in general or their charity profile in particular https://give.org/. Not all worthy nonprofits have information in the last three, but the first two are gold.