There's a piece of folk wisdom left over from decades past that says home equity interest is deductible, full stop. Plenty of people still run their math on it. The rules changed in 2018, and the honest answer today is: for how this site uses a line, the interest usually isn't deductible, and the strategy should never have leaned on the deduction anyway.
Current federal rules only allow the deduction when the borrowed money buys, builds, or substantially improves the home securing the line. Renovate the kitchen with a HELOC draw and that interest can qualify. Use the line for paycheck parking, chunking a car loan, or covering expenses between paydays, and it doesn't, no matter that your house secures the debt. What matters to the IRS is where the money went, not where it came from.
And even the qualifying interest only helps if you itemize. The standard deduction is large enough now that most households never do, which turns the whole question academic for them.
Here's why I say that's fine. This strategy does its work by cutting the interest you owe, mainly through average daily balance mechanics and disciplined chunks. A deduction only refunds a slice of interest you actually paid. Paying less interest beats deducting some of it every time the choice exists. If your chunk math only works when a tax deduction props it up, the math doesn't work.
If you do use part of a line for genuine home improvements, keep records showing which draws went where, because mixed-use lines get messy at tax time. And I'm a licensed insurance broker, not a CPA, so before you claim anything, put your actual numbers in front of a tax professional who can look at the whole return.