A “wash sale” happens when you sell an investment but then buy it again (or buy a very similar one) within 30 days. If you do that, you can’t deduct any capital losses that you incur from that transaction when you file your taxes.
You don’t have to sell and buy with the same investment advisor or brokerage for a sale to be considered a wash sale. So if you sell an investment from a non-Ellevest account and then buy the same (or similar) investment with Ellevest, that’s still a wash sale.
You can read more on the IRS website here.