What Year-End Tax Moves Should You Make Before December?
The tax moves that lower a bill for the year have a hard deadline of December 31. Most of the ones worth making also take time to get right, since they depend on where income actually lands and how that compares to later years. That is why the real work happens in the fall rather than in December. A review in October leaves enough room to model the options and act deliberately, instead of forcing decisions in the final weeks of the year.
Why does year-end matter more than filing season?
By the time a return is filed in the spring, the year it covers is already closed. Almost nothing can be changed after December 31. A Roth conversion has to happen inside the calendar year to count on that year's return. The same applies to a loss taken on an investment, or a charitable gift. Starting the review in October leaves roughly ten weeks to run projections and act while there is still room to adjust. That head start is where most of the value in year-end planning actually lives.
How does a Roth conversion fit into a lower-income year?
A Roth conversion moves money from a pre-tax retirement account into a Roth account, and the tax gets paid now instead of in retirement. The reason to do it in a particular year usually comes down to bracket space. For 2026, a married couple filing jointly stays in the 12% bracket up to $100,800 of taxable income, and the next dollar is taxed at 22%. In a year when income dips, often after retiring but before Social Security and required distributions begin, there can be room to convert a meaningful amount at a lower rate than the account holder is likely to face later. Converting $40,000 in a year with space under the 22% breakpoint, as one example, locks in that lower rate on money that might otherwise come out higher.
The conversion is not free. Because the tax is due in the year of the conversion, it only makes sense when the current rate is lower than the expected future rate. That case is often strongest for a surviving spouse, who usually files as a single taxpayer and reaches higher rates on less income. This is why a conversion gets modeled against a household's full projected income rather than run on a round number.
What is tax-loss harvesting, and where do people trip up?
Tax-loss harvesting means selling an investment in a taxable brokerage account that has fallen below its purchase price, so the loss can offset realized gains, plus up to $3,000 of ordinary income beyond that. It only works in a taxable account, since gains and losses inside an IRA or 401(k) are not reported year to year. The common mistake is the wash-sale rule. If you buy the same or a substantially identical security within 30 days before or after the sale, the loss is disallowed. That window catches people who sell a fund and buy it back a week later, and it also catches investors whose accounts reinvest dividends automatically, since that reinvestment counts as a purchase. A loss that is not needed this year is not wasted either, since unused capital losses carry forward. Harvesting can be done without pushing a portfolio off its target allocation, as long as it is planned around that 30-day window instead of rushed at year-end.
Which income thresholds deserve a second look?
A move that looks smart on its own can cost money elsewhere, so a few thresholds are worth watching. The first is IRMAA, the income-related surcharge on Medicare premiums. For 2026 it begins at $218,000 of income for a married couple and $109,000 for a single filer, and it is based on the tax return from two years earlier. IRMAA works as a cliff, so crossing a threshold by even a small amount can trigger the full surcharge for that tier. A large conversion this year can raise a Medicare premium two years from now, when the surcharge is set from this year's return.
The second is the standard deduction, which for 2026 is $32,200 for a married couple filing jointly. Whether a household itemizes or takes the standard deduction changes whether charitable timing and other deductible expenses actually reduce the tax bill, so it helps to know that answer before making moves that depend on it.
Where does charitable giving fit in?
Giving is one of the most flexible year-end levers, and it has enough moving parts to deserve its own discussion. Click here to read the full guide to year-end charitable giving, which covers qualified charitable distributions, donor-advised funds, and the bunching strategy.
The households that benefit the most from year-end planning are the ones who look at the current-year picture in the fall, while projections can still change and there is time to act. Oasis works through these decisions with clients before year-end, and fall is the right time to begin.