The 7% rate didn't start until 1/1/23.  For last year, it averages 5%.  I always have to look it up, but I think IRS by statute (not regulation) doesn't have to pay any interest if the refund is authorized within 45 days; otherwise, it goes back to the due date of the return, even if filed late.  

Interest Categories 4th Quarter(Oct-Dec) 3rd Quarter(Jul–Sep) 2nd Quarter(Apr–Jun) 1st Quarter(Jan–Mar)