The IRS is serious about deadlines. In a new case, the U.S. Tax Court upheld penalties against a taxpayer for not filing tax returns on time. He filed an extension for 2 years and filed his returns 3 days after the extended due dates. The tax code imposes an addition to tax for failing to timely file a return. For a late filing of not more than a month, it’s equal to 5% of the tax required to be shown on the return. The court stated the taxpayer didn’t explain his late filings or show they were “due to reasonable cause and not willful neglect.” (TC Memo 2018-126)