[gamblor956]

If your return is complicated enough that you need CPAs and lawyers to handle it, the IRS won't be able to give you a ready return of what it thinks you owe because it doesn't have access to all of the information it would need to do that.

I end up missing documents that somehow the IRS knows about but the institutions neglect to provide.

The IRS knows about these because your counterparties to these transactions filed their own documents, and you were reported in these documents in some fashion. If you are failing to file those documents, that is absolutely a failure of your tax advisors to properly handle your compliance, and you should absolutely demand they make you whole for penalties and interest owed on these failures, and sue them for malpractice if they do not. (99% of the time they will just pay you without needing a lawyer to get involved, though this might come in the form of a credit against current/future services if you are still a client.)

[SnowHill9902]

It CPAs are external they may not even be aware of said documentation.

[gamblor956]

That would literally be malpractice.

If the CPA is aware of the transaction, then they are aware that the documentation by the counterparties exists (or should exist), and of their client's legal responsibility to file similar documentation.

If they are not competent to handle the compliance associated with an M&A transaction, then they have no business providing accounting services to a client that engages in M&A transactions regularly.