Improving Assistance for Taxpayers Act This bill requires the Internal Revenue Service (IRS) to respond to Taxpayer Advocate Directives within specified time frames. In the case of a Taxpayer Advocate Directive issued by the National Taxpayer Advocate (NTA) pursuant to a delegation of authority from the IRS, the IRS Commissioner or a Deputy Commissioner must modify, rescind, or ensure compliance with the directive within 90 days. If a directive is modified or rescinded by a Deputy Commissioner, the NTA may appeal to the Commissioner. Within 90 days of the appeal, the Commissioner must either ensure compliance with the directive or provide a description of the reasons for any modification or rescission made or upheld pursuant to the appeal. The bill also requires the NTA annual report to identify any directive that was not honored by the IRS in a timely manner, as required by this bill.