The Survivor Tax Filing Simplification Act directs the Secretary of the Treasury, in consultation with the Social Security Administration, to establish an online Survivor Tax Portal within 12 months. This portal aims to assist surviving spouses and estate executors in preparing and filing various tax returns, including estate tax returns, joint returns, and individual returns for surviving spouses. The portal will offer clear guidance through checklists, pre-populated forms, and status updates, alongside secure uploading of legal documents. It will integrate relevant death information from the Social Security Administration and incorporate robust safeguards to protect personal data and ensure authorized access. Additionally, the bill mandates the publication of an annual instructional guide for the portal, to be attached to Social Security Benefit Statements. It also establishes a grant program to help states improve their recordkeeping and reporting of death information to the Social Security Administration, prioritizing those that enhance the portal's efficiency.