In most states, a paycheck has two income tax withholdings: federal and state. In Florida, it has one. Florida does not tax the income of individuals, so the only income tax your Tampa employer withholds is federal.

That sounds like good news, and it mostly is. But it also means there is no state withholding system to notice that something is off, no state return that comes back with a balance due as an early warning. If your federal Form W-4 is wrong, the federal balance due is the first sign of trouble. And if the trouble repeats, the IRS can tell your employer how much to withhold. That is called a lock-in letter.

Why Florida workers under-withhold

A few patterns come up constantly in Tampa:

  • Two-income households. Each spouse’s employer withholds as if that job were the only income. Combined income lands in a higher bracket than either job’s withholding assumed. The Form W-4 has a step specifically for multiple jobs or a working spouse, and many people skip it.
  • Side income. A W-2 job plus freelance, rideshare or rental income, with nothing withheld on the side income and no estimated payments.
  • Bonuses and commissions. Tampa’s sales, finance and real estate workers often see irregular pay where withholding does not keep up with the final tax.
  • New residents. People who move from a state income tax state sometimes reset withholding in the move and never revisit it.

Florida’s lack of an income tax does not cause any of these problems. It just removes a second system that might have flagged them.

How the Form W-4 works

IRC 3402 requires employers to withhold income tax from wages, and the employee’s Form W-4 tells the employer how. The current W-4 asks for filing status, multiple jobs or spouse works, dependents, other income, deductions and any extra withholding per pay period. There is no Florida equivalent to complete.

Retirees are in the same position. Pension and annuity payers withhold federal income tax based on Form W-4P, and nonperiodic distributions such as IRA withdrawals use Form W-4R. A Tampa retiree who moved from a state with income tax may find that the old pension withholding election was set up with both federal and state taxes in mind. After the move, it is worth confirming that the federal withholding alone is enough, especially when Social Security and required minimum distributions push total income higher than expected.

The IRS Tax Withholding Estimator on irs.gov walks through the same inputs and produces a recommended W-4. For two-income households and people with side income, running it once a year is the simplest way to avoid a surprise.

What a lock-in letter is

The IRS runs a Withholding Compliance Program, described in IRM 5.19.11. When the IRS determines that an employee’s withholding is substantially inadequate, it can issue a lock-in.

Under IRM 5.19.11.3.9:

  • Letter 2800C goes to the employer. It instructs the employer to disregard the employee’s Form W-4 and withhold at the filing status and rate the IRS specifies.
  • Letter 2801C goes to the employee. It explains the instruction and invites a response.
  • Timing. The employer must start the lock-in beginning with the first pay period ending on or after 60 days from the date of the letter.

The employee letter asks for a response within 30 days if the employee wants to request a modification, and the IRM describes a 60-day window before the case moves to the next step.

After the lock-in

Once a lock-in is in place, the employer must follow it. A new Form W-4 that would reduce withholding below the lock-in rate is disregarded. But under the IRM, an employer must honor a Form W-4 that results in more tax withheld than the lock-in requires. You can always choose to withhold more. You cannot unilaterally withhold less.

To change the lock-in, you go back to the IRS. IRM 5.19.11.7 describes modification: a taxpayer may call or send additional information and ask the IRS to reconsider a proposed or existing lock-in determination, changing the filing status or withholding rate. When the taxpayer calls, IRS staff are directed to complete the withholding estimator during the call. Bring real numbers: recent pay stubs, your spouse’s income, dependents, other income.

The estimated tax penalty

Under-withholding usually comes with a penalty. IRC 6654 imposes an addition to tax when withholding plus estimated payments fall short of the required annual payment. The required annual payment is generally the lesser of 90 percent of the current year’s tax or 100 percent of the prior year’s tax, rising to 110 percent of the prior year for higher-income taxpayers.

One quirk helps. For the 6654 penalty, income tax withheld from wages is generally treated as paid evenly through the year unless you elect otherwise. That means increasing withholding in October can reduce a penalty that would not be reduced by an estimated payment made in October. If you realize mid-year that you are short, a W-4 change can do more than you might expect.

Penalty relief is a separate subject, covered in my guide on penalty abatement in Tampa.

Balances that already exist

Fixing withholding prevents next year’s problem. It does not pay this year’s balance. If you already owe, the usual options apply: pay in full, a short-term extension, or an installment agreement. See installment agreements in Hillsborough County. The IRS will generally expect current-year compliance as a condition of any agreement, which means withholding has to be fixed anyway.

If you also have self-employment income, withholding on your W-2 job can be increased to cover the tax on the side income, instead of making quarterly estimated payments. My guide on self-employed tax problems in Tampa Bay covers the estimated tax side.

A two-income illustration

Consider a hypothetical Westchase couple. One spouse earns a salary at a downtown firm. The other earns a similar salary at a hospital. Each filled out a Form W-4 as married filing jointly and left the multiple jobs step blank.

Each employer therefore withholds as though its paycheck were the household’s only income, which places much of each salary in lower brackets for withholding purposes. Combined, their income is taxed at higher marginal rates than either employer assumed. In April, they owe several thousand dollars. They pay it, but they do not change the W-4s. The next year, they owe again, plus an estimated tax penalty under IRC 6654.

After a pattern like that, the IRS can review the withholding and, if it finds it substantially inadequate, issue lock-in letters to one or both employers. A lock-in would fix the under-withholding, but on the IRS’s terms rather than theirs.

The couple could have avoided the whole sequence with one evening and the IRS Tax Withholding Estimator, or by checking the multiple jobs box on both forms. Florida’s lack of a state income tax did not cause the problem. It just meant there was no state balance due to make them look at their paychecks sooner.

Practical steps for Tampa workers

  1. Run the IRS Tax Withholding Estimator after any change in jobs, marriage, a second income or a large bonus.
  2. If both spouses work, complete the multiple jobs step on the W-4 for each job, or add extra withholding.
  3. If you receive Letter 2801C, read it the day it arrives. You have a limited window to respond before the lock-in takes effect.
  4. If the lock-in rate is too high for your real situation, request a modification with documentation.
  5. If you owe now, get on a plan and fix withholding at the same time.

GetIRSHelp.com has more on IRS installment agreements.

Florida gave you one less withholding line on your paycheck. Make sure the one you have left is right.