Year-end tax questions to settle with a CPA before December 31

December 31 closes some tax decisions and leaves others open. A Roth conversion, a charitable gift, and the paycheck that funds a workplace retirement deferral generally have to be finished in 2026 to count for 2026. The fourth estimated-tax payment for a calendar-year individual is not one of them. On the 2026 Form 1040-ES it is due January 15, 2027. The useful late-October meeting sorts your list onto those two dates.

What has to be finished this year

A Roth conversion counts in the year it is completed. A conversion done in January is the next year’s income. A conversion to a Roth IRA made after 2017 cannot be recharacterized, so it is final once the custodian moves the money. The IRS states that rule in its IRA frequently asked questions and in the instructions for Form 8606. Ask the CPA to size the conversion before you request it, including whether it changes a credit, a surcharge, or the tax on other income.

Employee deferrals into a workplace plan come out of this year’s wages. If the last payroll of 2026 has already been processed, there is no remaining paycheck to defer from. Ask what has been withheld so far and what the plan will still accept. An IRA contribution uses a different clock. For most people it can be made until the filing deadline without an extension. A CPA who gives you one date for “retirement contributions” has mixed two rules.

A charitable gift counts when it is completed. A check you mean to mail, or shares a broker has not yet transferred, is not yet a 2026 gift. If you are required to take a minimum distribution this year, the ordinary deadline is December 31. The first year a distribution is required, and many inherited accounts, use a different date. Ask which date applies before you plan to repair a missed distribution in January.

Equipment follows the same idea. A deduction that depends on placing an asset in service needs the asset ready and available for its use this year. A purchase order dated in December is not that fact. The percentage and the dollar limit change often enough that the CPA should apply the current rule to the specific asset.

Estimated tax is the January date

For 2026, Form 1040-ES lists four due dates for a calendar-year individual: April 15, June 15, September 15, and January 15, 2027. You can skip the January 15 payment if you file the 2026 return by February 1, 2027, and pay the entire balance due with that return. Filing in April does not replace the January payment.

The same form states the general rule. You usually must pay estimated tax for 2026 if both of these are true. You expect to owe at least $1,000 after subtracting withholding and refundable credits. And you expect withholding and credits to be less than the smaller of 90 percent of your 2026 tax or 100 percent of the tax on your 2025 return. The 2025 return has to cover all 12 months. If your 2025 adjusted gross income was more than $150,000 ($75,000 if your 2026 filing status is married filing separately), use 110 percent of the 2025 tax instead of 100 percent. Farming and fishing income uses a different percentage. These are thresholds from Form 1040-ES, not your payment. The CPA still has to apply them to the withholding already taken out.

Income that arrives late in the year does not always require the same installments as income you earned all year. Form 1040-ES points to the annualized income installment method in Publication 505, figured on Form 2210. Ask whether your facts support it, and which items they would annualize. “Your estimates are probably fine” is not that computation.

If you also have wages, the form says you may cover other income by filing a new Form W-4 so your employer withholds more. Pension and annuity withholding uses Form W-4P. Ask whether extra withholding changes the January number before you submit either form. If you mail a payment, the 2026 Form 1040-ES says the postmark that counts is the date the Postal Service processes the piece, which may not be the day you dropped it in a mailbox. Paying from an IRS online account or with Direct Pay leaves a confirmation number. Keep it.

What to bring to the meeting

Bring the 2025 return, year-to-date withholding, and any estimated payments already made, with dates and confirmation numbers. If you have a business, bring a year-to-date profit and loss and a list of what you might still do: a sale, a conversion, a gift, a retirement contribution, or equipment. If you do not have those reports, say so. That gap is part of the scope.

Questions worth asking in that meeting:

• Which items on this list have to be finished by December 31, 2026, and which can wait until I file?
• Do I still owe the January 15, 2027 estimated payment, or does filing and paying the balance by February 1, 2027 remove it?
• Are you testing 90 percent of this year’s tax, or 100 or 110 percent of last year’s, and what is still unpaid?
• If income was uneven, will you compute the annualized installment on Form 2210?
• Would extra withholding change the answer, and which form does that go on?

A useful answer is a date and a remaining amount, or the name of a document they still need. A meeting that ends with “we will see at filing” has not planned the year.

Where to look for that CPA

Tax planning and tax preparation are different lines on a listing. Search CPAs who list tax planning. If the open questions are an owner’s pay, a retirement plan, and the books, start from the small-business specialty. A household question that is mostly wages, investments, and a conversion sits closer to individual tax. An S corporation or LLC still has payroll, basis, and owner draws to settle, which is a separate hire from this year-end list. How to choose a CPA for an S corporation or LLC covers that conversation. Find a CPA and read the services on the profile before you send a year’s records to anyone. City pages include Lake Havasu City and New York. What a fee covers is in how much a CPA costs for taxes.