​If I commit to donating 1% of sales to charity, do I have to prove that I am?

I sell a bulk product that certain non-profits could use. I want to donate 1% of sales plus all my unopened returned items (about another 1%), so in reality, I plan on donating more than 1%, but I’m just wondering if I should keep a very detailed account of how much I’m donating in case someone asks to see proof. Is that necessary?