https://academy.binance.com/en/articles/what-is-busd

The accounting firm Withum completes these audits as part of BUSD’s requirements as a regulated cryptocurrency. Not every project does this, and some fiat-backed stablecoins might not have all the reserves they claim.

For example, a case brought by the New York Attorney General indicated that the reserves for the stablecoin Tether (USDT) were not 100% fiat-backed. This discovery was in direct contradiction to previous statements made by Tether.