If an entity fails the Qualified Opportunity Zone business tests, it is subject to the 90% of assets test. If the 90% of assets test fails, then a penalty is calculated. There is a monthly penalty. The penalty under IRC section 6621(a) (2) is 3% plus the fed short-term rate. Currently, the rate is 5% a year. 90% of assets less qualified assets times the 6621 rate. Here is a 90% test penalty example: total assets $50,000,000, 90% of assets are $45,000,000, total qualified assets $40,000,000, there is a $5,000,000 shortfall. The monthly penalty is $20,833.33, $5,000,000 X (5% /12). If there is a penalty, the shortfall will be recalculated each month.