About $47k taxable (6 stocks, 2 ETFs), 401k with target date fund, Roth at 80/20 VTI/VXUS. Rebalancing used to take a full afternoon every quarter because of the tax lots in taxable.
Few weeks back I set up a small job on a cloud machine. Pulls holdings, runs drift calcs, spits out trades with estimated tax impact. Runs overnight.
The thing that got me: it sorts every lot by holding period and builds the sell list clearing long term gains first. Flagged one lot that was 3 days from crossing one year. Wouldn't have caught it manually.
Not sure the tax estimate is perfectly accurate but close enough for what I need.
Was letting drift hit 7 or 8% just because the spreadsheet was annoying, not for any strategy reason. Now I check the report over coffee.
Wash sale tracking is probably next. I sold some VTI in taxable in April and then bought in my Roth within the 30 day window without thinking. December is going to be the real test.