1. You should have known all along that you were not having any federal income taxes withheld by checking your pay stubs. You had the whole year to raise this as a concern.
2. To know if the employer made a mistake with the withholding calculation, you would have to look at one of your individual pay stubs to see what the withholding calculation should have been, using the tables and instructions in IRS publication 15-T.
3. The W-4 requires that you take into account any second jobs you had, or if you are married, the job or jobs your spouse has. If you are married, and did not take your spouse's job into account, that could result in very low withholding for your job (that would be correct in a married household with only one working spouse, but is too low if both spouses work). Without seeing the actual W-4, your pay stubs, and your spouse's info (if any), it's impossible to see where the mistake was made.
4. You may want to file a new W-4. Try using the IRS estimator to figure out what you should actually claim.
https://www.irs.gov/individuals/tax-withholding-estimator
5. If Turbotax wants to add an under-payment penalty, try and decline the offer. Pay as much as you can when you file, and pay the rest as soon as you can. If the IRS sends you a bill for a penalty, you can apply for a waiver (abatement) for cause or if this is your first time owing a penalty. It is harder to apply for penalty relief if you have already voluntarily paid the penalty.
6. If you owe taxes and can't pay in full right away, don't ask for a payment plan unless you know it will take past August to pay it off. The payment plan application has a non-refundable fee that is more than the interest and late fees you would pay as long as you can pay off the tax before August. If you can't pay in full right away, tell turbotax you will "pay by check". Pay as much as you can electronically at www.irs.gov/payments, and then keep paying whenever you can to pay it off. Make sure to select "2023 form 1040" as the reason for the payments.
