Is it neccesary to have my audit done at the higher PCAOB level?
However, PCAOB level audits are required to be listed on the major two exchanges (NASDAQ, NYSE). For a Reg A+ IPO to the major exchanges, the offering starts as a simple Reg A+ and then just prior to the time of listing the format of the Reg A+ Offering Circular is changed (the content remains the same) to have a similar layout as an S-1. For these IPOs, companies are required to file a PCAOB audit for the last quarter prior to listing. And a series of filings are made post-listing by the securities attorney that have the effect of upgrading the SEC filings to that of a full reporting public company on a major exchange.
Note that listing your company via Reg A+ on the OTCQB or OTCQX does not require PCAOB. In this case, the audit obligation is the same as for the Tier 2 Reg A+ - once per year US-GAAP. This is a significant advantage for companies that used Reg A+ to list on these exchanges.
PCAOB audits are more expensive than US-GAAP audits.