If you set up estimated tax payments and then your income situation changes, can you stop or change the payments?

[AnthonyC]

Yes, you can (and its quite common to do so when your income situation changes)

The program produces these forms as a convenience for you to make the payments.  You are not locked into those payments.  The program will produce them automatically if you owed tax as the government requires you to withhold enough tax to cover your tax liability or make estimated tax payments.  If you don't have enough withholding and you don't make estimated tax payments, then the IRS or your state can charge you with an underpayment penalty.

If you owed tax this year because of a one-time event and you won't owe next year, then you can decline to send any payments.  You can also decline to send the payments even if you will owe tax next year, but you may be assessed an underpayment penalty.  You can also adjust the amount of the payment at any time (higher or lower depending on anticipated income during the year) and you can pay directly online or just change the payment amount on the forms you already have printed. 

https://www.irs.gov/payments