I’m 62, single, retired with $800k. Which accounts should I use first for living expenses?

To fully diagnose, I’d need some additional information but I can give you some things to consider.

While it may go hand in hand with other pieces of the decision, I’d want to understand your Social Security benefit and when you are considering claiming it and if that will cover your expected expenses in the future.

As far as spending until you claim Social Security, I’d want to know more about the inherited IRA.  Is it subject to annual distributions and the requirement to have it closed?  If so, this will be money you can use for your monthly expenses.  If you’re not having to take distributions annually, but are still required close it in 10 years, it can make sense from a tax perspective to spread withdrawals out over multiple years versus waiting until year 10 and taking it all at once.  Also withdrawing it prior to Social Security could make sense from a tax perspective.

If the inherited IRA is from a spouse you could consider moving it to an IRA in your name.  You could then use the funds or consider doing Roth conversions while your income is low.

You’ve got a prime opportunity to do tax planning that could help extend how long your money will last.  You don’t want to waste these years of no taxable income.  I’d recommend finding a fiduciary planner that will work with you on either a 1-time or ongoing basis.  The value they could provide given your situation could easily be worth the cost.