Disaster Tax Relief Act of 2021 This bill sets forth tax relief provisions for taxpayers residing in a disaster zone. Specifically, the bill allows penalty-free qualified disaster distributions from tax-exempt retirement plans up to $100,000; allows recontributions of distributions for home purchases cancelled due to disasters; increases to $100,000 the limit on loans from retirement plans not treated as distributions; allows an employee retention tax credit for 40% of wages paid by employers affected by a disaster; expands eligibility for disaster-related personal casualty losses; allows exclusions from gross income, for income tax purposes, of amounts received from state-based catastrophe loss mitigation programs and emergency agricultural assistance; suspends the limitation on corporate charitable contributions; allows the Small Business Administration to award grants to accomodate extraordinary occurrences having a catastrophic impact on small business concerns; and allows a new tax credit for 30% of qualified wildfire mitigation expenditures.