There are times when IRS can go back more than three years to seek taxes. If more than 25% of gross income is omitted from a return, then the Service has six years to assess the tax, unless the filer disclosed the omission on the return. Here, an S corporation understated its gross receipts on Form 1120S by over $800,000 for each of three years. As a result, its sole owner underreported income from the firm on Schedule E of his Form 1040 by the same amounts. IRS sent out deficiency notices after the usual three-year limitation period but before the end of the six-year period. The gross receipts omission wasn’t adequately disclosed on the S corporation’s 1120S or the owner’s individual return, the Tax Court says (Manashi, TC Memo. 2018-106).