Commonsense Reporting Act of 2017 This bill amends the Patient Protection and Affordable Care Act and the Internal Revenue Code to modify the requirements for employers to report health insurance coverage information to the Internal Revenue Service (IRS) by the end of the tax year. The bill changes the information that is required and permits employers to voluntarily report the information prior to the beginning of open enrollment. The Department of the Treasury must develop a prospective reporting system to permit: employers to voluntarily report specified health insurance coverage information before the annual open enrollment period; the exchanges, the Federal Marketplace Data Services Hub, and the IRS to access the information to carry out their missions and provide the Department of Health and Human Services with information related to eligibility for advance payment of premium tax credits and cost-sharing subsidies; the exchanges to communicate with employers and employees regarding eligibility for the tax credits or cost-sharing subsidies; and employers to provide updates to the hub regarding changes in coverage for employees. At the time of enrollment, exchanges must provide employers the names of employees and dependents that enroll in a qualified health plan for a year. If a health insurance issuer or employer is unable to obtain the taxpayer identification number of a dependent, Treasury may permit the individual's full name and date of birth to be used instead. Employers participating in the reporting system established by this bill are exempt from the requirement to report health insurance coverage information to the IRS by the end of the tax year.