Source: Enhancement Act (passed by Senate 4/21 and House 4/23)
This Act added $310 billion to the PPP loan program. It also attempted to answer some open questions from the quickly thrown-together CARES Act. (Many questions remain).
Significant is the answer on federal employer payroll taxes: These are not allowed to be considered in the PPP loan applied for. By example, if the employee gross payroll was $4,000 per month, the loan maximum would be $4,000 * 2.5 months = $10,000 without regard to the federal employer tax on that amount.
Can the employer consider these taxes when applying for debt forgiveness: No answer yet, however it is unlikely that it would be allowed. (Under IRC Section 265, deductions are not allowed for expenses relating to tax-exempt income (such as the amount of the PPP loan forgiven)).