[ncfool]

I would pay what you owe me nothing more. There is no penalty as long as you pay in what you owe

[Aliska]

There is a penalty for failing to file an estimate and failure to pay estimated taxes.

https://www.irs.gov/businesses/small-businesses-self-employed/estimated-taxes

I've gotten dinged on it in the past and still do if at tax time I have over a certain amount of income even though I qualify as a farmer and don't have to file and pay estimates if they file and pay by March 1. Also same rule for fishermen but not business entities. I have a good CPA.

The IRS would probably argue if contested that you had the windfall and should have paid it out of that.