After all the interruptions and bluster and defensiveness, it's weird how quiet Trump was the whole time Hillary questioned his finances and refusal to release his tax returns.
If he
is having his finances audited it means he cannot release the tax returns until that process is completed as I understand this is the process in the USA also for submitting a full set of accounts which has been checked by a certified accountant. The IRS I understand will also audit as small percentage of tax returns it receives. It's not clear if his accountant has these of the IRS does. I haven't seen the recording of the debate yet.
There is also nothing to prevent him releasing figures before such an audit is done, but it is common practice to wait until the tax authority has concluded its audit.
If there are old accounts going back a few years and unaffected he could release these which applies to many of his companies.