You can deduct any home improvements that you can prove. You don't necessarily need receipts; photos, contracts, statements from contractors, or affidavits from neighbors, may be enough to convince the IRS that you actually did work. Please note that swimming pools are a bit tricky:
Real estate experts estimate that an average 14x28-foot inground concrete pool potentially adds 5 to 8 percent to the real estate value of your home. If your property is worth $400,000, you'll realize a boost to the value of your property of about $20,000 to $32,000.
This was their "take" and approach for adding improvements to the original cost basis upon sale of a residence. Anything else should be a good faith best and closest accuracy estimate of cost when the costs were incurred.
