Use your 2025 tax return to improve your 2026 plan. Separate last year’s results from this year’s withholding, income and planned transactions.
April 6, 2026 · Financial Forte Staff
Historical article: prepared retrospectively using information available as of April 6, 2026.
Once a tax return is filed, it is tempting to put the folder away until next year. The completed return can do more than document what happened. It can help identify which income sources, payments and deductions deserve attention while there is still time to make decisions for the current year.
Use the return as a starting record, then update the assumptions. A 2025 result is not a complete 2026 projection. Income may change, one-time transactions may disappear and provisions beginning in 2026 may affect the next return differently.
Explain the result before changing the plan
Separate total tax from the amount paid with the return or received as a refund. A balance due can reflect insufficient payments rather than an unexpected increase in the tax rate. A refund can reflect withholding, estimated payments or refundable credits rather than a reduction in total tax. [1]
Compare income categories, deductions and payments with the prior year. Ask which changes are recurring. A large investment sale, Roth conversion or business payment may explain much of the difference, while a pension starting late in the year may have a larger effect during the following full year.
Keep the explanation brief enough to use. “Tax rose because of additional taxable retirement income, while withholding stayed unchanged” is more actionable than simply recording that the balance due was disappointing.
If the return appears incorrect, address that separately with the preparer. Planning from an unresolved error can carry the problem into another year. Retain corrected records and supporting calculations with the final version used for planning.
Update payments using a full-year projection
Suppose a household’s 2025 total federal tax was $14,000 and payments were $11,000. The $3,000 balance due was paid with the return. That payment settles the illustrated prior-year balance; it does not count as a payment toward 2026 merely because it was made during 2026.
After reviewing expected income, the tax professional projects $16,000 of federal tax for 2026. Existing withholding and estimated payments are projected to total $13,000. The new projected gap is again $3,000, but it comes from the current year's facts rather than automatically copying the old balance due.
If the household chooses to address that entire projected gap through eighteen remaining equal payrolls, the additional withholding would be approximately $166.67 per payroll ($3,000 divided by eighteen). The actual election needs to reflect payroll timing and the amounts already withheld. A household using estimated payments instead needs to consider the applicable installment dates and payment rules. [2]
This calculation does not establish whether an underpayment penalty applies or whether a safe harbor is satisfied. Payment timing, prior-year tax, income and other facts matter. Ask the preparer to distinguish the expected final bill from the amount and timing needed to meet payment requirements. [2]
Schedule a check of the first paycheck on which the change should take effect, comparing the deduction with the revised election. A plan to withhold more is useful only when payroll actually implements it.
Review transactions before they occur
A completed return can help frame a discussion about a future investment sale, retirement withdrawal or Roth conversion. Estimate the transaction's effect on the whole return, including deductions or income-related costs, rather than applying the last observed marginal rate mechanically. [1][3]
For example, the enhanced senior deduction has income-based limits. Additional income can reduce the deduction for an otherwise eligible taxpayer. A conversion may therefore affect taxable income through more than the converted amount alone. Eligibility and the modified-income calculation should be checked before acting. [3]
Medicare income-related premiums use their own rules and generally look to tax information from an earlier year. A transaction's premium effect can therefore occur later than its tax effect. A future-year premium threshold that has not been announced should not be treated as a known number. [4]
Also identify rules that differ between 2025 and 2026. The federal charitable deduction for eligible nonitemizers begins in 2026, while the new senior deduction began in 2025. A contribution or gift should be evaluated under the rules for the year in which it is made, not simply the year of the return currently on the desk. [3][5]
Choose a few actions with dates
The return may reveal several planning opportunities, but trying to complete all of them at once can leave the important ones unfinished. Select the actions most connected to a known change: update withholding after a pension starts, estimate the tax on a planned sale or review a contribution election after income changes.
Give each action an owner, a target date and a way to confirm completion. Keep an unresolved tax estimate separate from an approved transaction instruction. Share the dated projection and expected transaction amounts so an adviser and tax preparer can work from the same assumptions when their recommendations interact.
Schedule another review when a material event occurs or later in the year while options remain available. Waiting until the final days of December can limit the time to gather records and complete account processing.
A useful post-filing conversation ends with an explanation of last year's result and a short plan for this year's decisions. The return supplies evidence. Your expected income, spending needs and goals determine what to do with it next.
Related reading
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Educational information, not personalized investment, tax, legal or benefits advice. Examples use hypothetical assumptions. Verify current rules and your circumstances before acting.
Sources
- [1] IRS 2025 Form 1040 and 1040-SR instructions — February 25, 2026 revision
- [2] IRS Publication 505: Tax Withholding and Estimated Tax (2024) — March 5, 2024
- [3] Public Law 119-21 — Section 70103: Temporary senior deduction — July 4, 2025
- [4] 20 CFR 418.1135: Which tax year is used for income-related Part B premiums? — April 1, 2023 edition
- [5] Public Law 119-21, sections 70424–70425: charitable deductions — Enacted July 4, 2025
