You have probably used the short method in years past instead of the annualized installment method you are using this year.
If all the income and withholding and estimated taxes paid were earned and paid evenly throughout the year, you should be able to use the short method instead of having to complete the annualized method.
For additional information, please refer to the following link:
IRS Instructions for Form 2210
The line-by-line instructions are very helpful for how to complete the annualized installment method of Form 2210.
[Edited 03/01/2021|6:45 pm pst]
