Yes, the tax bill can be substantial, and it is worth planning with a CPA well before the sale. After decades of ownership, the gain (sale price minus the original purchase price and documented improvements) can be enormous because the basis is so low. The main relief on a primary residence is the capital gains exclusion, which lets a qualifying single owner shield a portion of the gain and a married couple roughly double that, provided the ownership and use tests are met. Anything above the exclusion is generally taxed as a long-term capital gain, at lower rates than ordinary income, though the exact rate depends on your total income and can bring additional considerations at higher levels. On a home bought in the late 1960s that now sells for seven figures, the taxable gain can easily run past the exclusion, so the bill is real even at long-term rates. Two practical moves: - Gather records of every capital improvement you can document. Improvements raise your basis and lower the gain. - Work with an experienced agent who coordinates closely with a CPA, because timing, improvement documentation, and how the sale is structured can meaningfully change what you owe.