If you didn't pay at least 90% of your taxes owed (or 100% of last year's tax liability) and owe more than $1,000 when you file your taxes, you may be charged a fine called the underpayment penalty
Did the IRS send you a letter and bill? Or did the penalty show up on your return 1040 line 38? If you haven't filed yet you can try to reduce or eliminate it.
If you do not pay enough tax, you may have to pay a penalty for underpayment of estimated tax. Even if you are getting a refund you can still owe a penalty for not paying in evenly during the year. Generally, most taxpayers will avoid this penalty if they owe less than $1,000 in tax after subtracting their withholdings and credits, or if they paid at least 90% of the tax for the current year, or 100% of the tax shown on the return for the prior year, whichever is smaller. It is included in your tax due or reduces your refund.
It's not for filing or paying late. It doesn't have to do with last year's tax return or not paying estimates for this year. The penalty is an "estimated" amount. It's a penalty if you owe too much or for not paying in enough withholding during the year or not paying in evenly. Even if you are getting a refund you can still owe a penalty. It's very common and normal and expected for the IRS or state to bill you for more or send you a refund.
The estimated tax penalty is based only on the current year. Past years or "a lifetime of paying taxes" have nothing to do with it.
Income tax is "pay as you go." You have to make payments periodically during the year, through either withholding or estimated tax payments. Paying a large amount at the end of the year does not satisfy the pay-as-you-go requirement.
As stated, the tax system is pay-as-you-go. Each year, you must pay into the system over the year, either through withholding or estimated payments. If you owe more than $1000 when you file your return, you can be assessed a penalty for underpayment, even though you got caught up by April 15. (There are some other conditions for an underpayment penalty, but the $1000 rule is the easiest to explain.)
If you switched from a job to self-employment, you need to make quarterly estimated payments. Or, if you retired, you need to increase your withholding from social security or your pension or retirement funds.
If this is the first time you have owed a penalty and you received a bill, you can request a waiver or relief for cause.
https://www.irs.gov/payments/penalty-relief-due-to-first-time-abate-or-other-administrative-waiver