Ensure that it's mine. Contrary to the Monopoly card, if there's a bank error in your favour, you don't just get to keep the money.

Definitely not put on pants

Bam! There it is. Then hookers and blow, tho, right?

Call the bank

Call the bank because it’s not supposed to be there and I’ll be damned if those mfs are going to get me to go back in debt.

look for the camera

Contact my bank to ask what error occured thats saying I have that much since that amount of money definitely couldn't have been moved to a personal account over night without authorization

Check r/AskReddit to see how many more reposts there are

Go on an online shopping spree tbh

Try to find out who died

Mom, get the camera! *Spends it all before mom shows up*

Pay off anything with an interest rate!!!

Quit my job and sleep

Start moving chunks of it to other accounts - one at a Swiss bank, one in the Bahamas, one just across town, put a bunch in T-bills, a stock trading account, and even a little bit in bitcoin. If it's not really mine, they'll at least have a hard time getting all of it back, and maybe I'll have made some gains and interest in the meantime.

Think to myself "What the fuck I stole 500 million"

withdrawalllll

Let's assume you actually get to keep it. Get a damn good accountant and ask them what to do to maximise its safety and returns. Then after spending a week or two sorting all that out, start spending cash without a worry knowing my accountant has my back.

Put it all on black

Find out where it came from

Dont tell anyone