What is the best way to prevent underpayment penalty when I sell lots of stock?

[crash345u]

If I sell stock and have a large gain ($80,000 of gain) when my total income is normally around $100K, how do I prevent underpayment penalties?

I  have withholdings on my $50K pension but would have to ratchet them up a lot to cover this kind of gain. Can I just take 15% of the gain and pay that in estimated taxes the same quarter that I sold the stock?

[AmyC · Accepted solution]

Yes that is exactly what the IRS wants. The IRS expects to be paid the same quarter you make the income. You can make estimated payments online at Payments.