Year-End Tax Planning for Small Business Owners: What You Can Still Do Before December 31
Every December, we hear from business owners who want to “do something” about their taxes before the year ends. Some of them still have real options. Others have waited until the only thing left is to report what already happened.
The difference is usually timing. Late October is a good moment to plan. You still have about two months, your numbers for most of the year are known, and there is time to set things up properly instead of rushing them through in the last week of December.
This guide covers the year-end tax planning moves that matter most for small business owners, why December 31 is a hard line for most of them, and when to start the conversation so you still have choices.
Why December 31 matters so much
Most owners treat tax season as something that happens in March and April. By then, the planning window has mostly closed.
Once the calendar turns, the year is largely locked. Payroll can’t be run retroactively. Retirement plans that needed to exist by year-end can’t be backdated. A purchase made on January 3 can’t be moved into last year.
In January, a good accountant can still report everything accurately and use the few options that remain open, such as certain retirement contributions that can be made up to the filing deadline. That work is worth doing, but it is cleanup. Planning happens before December 31.
That is why we encourage clients to think of year-end as the deadline for decisions, and tax season as the deadline for paperwork.
Move 1: Set up and fund retirement contributions
For many owners, a retirement contribution is the largest deduction available that doesn’t require spending money on something they don’t need. The money stays yours. It just goes into a retirement account instead of going to the IRS.
This is the move we look at first, and it’s also the one where timing trips people up most often.
Some plans have strict year-end requirements. With a Solo 401(k), for example, the plan generally has to be in place, and the owner’s deferral election made, by December 31 for the deferral to count for the current year. If you find out about this in February, it’s too late to use that part of the plan for last year.
Other contributions have more breathing room. Certain employer contributions can be made up to the filing deadline, which is one of the few options that stays open after year-end. But which contributions can wait, and which can’t, depends on the type of plan, your entity, and your income. Getting the plan set up early gives you the most flexibility.
A few questions to answer before December:
- Do you have a retirement plan for your business today, and is it the right type for your income level?
- If you have employees, how would a plan affect them?
- How much cash can you realistically put away this year without straining the business?
That last question matters. A retirement contribution only helps if your cash flow can support it. If your cash position is uncertain, that is a planning conversation in itself, and it’s one reason year-end planning works best when your books are current.
Move 2: Check S corporation payroll and reasonable compensation
If your business is taxed as an S corporation, this step is not optional. It is one of the most common places we find problems, and one of the easiest to fix if you catch it in time.
As an S corp owner who works in the business, you are expected to pay yourself a reasonable salary through payroll before taking distributions. Before year-end, we want to confirm three things:
- Your salary is defensible for the work you actually do.
- Payroll has actually run. Not just planned, not just recorded in the books, but processed with the proper withholding and filings.
- Your salary is set correctly against your distributions and your retirement contributions. These pieces are connected. Your salary affects how much you can contribute to certain retirement plans, and it can affect other deductions as well.
Fixing this in December is simple. Fixing it in March usually means amended filings and penalties.
There is another reason to look at payroll now. If you haven’t paid enough estimated tax during the year, adjusting your withholding through payroll before year-end can help close the gap. Withholding from wages is generally treated as if it were paid evenly throughout the year, which can make it a useful tool for reducing underpayment penalties. Our payroll services and estimated tax preparation work together for exactly this reason.
Move 3: Time purchases and expenses (only for things you already need)
This is the move people talk about most, and the one we approach most carefully.
If your business was already planning to replace equipment, a vehicle, or software in the first quarter, buying it and placing it in service before December 31 can move the deduction into the current year. That can be a smart use of timing.
The important words are “already planning.” A deduction reduces your tax. It does not make the purchase free. A $60,000 purchase made to save $15,000 in tax still costs $45,000. If the business didn’t need that equipment, you have spent $45,000 you didn’t have to.
Some practical points:
- “In service” means in use, not just ordered. A truck sitting at the dealership on December 31 generally doesn’t count for this year.
- Large purchases take time to arrange. Financing, delivery, and setup can easily take several weeks.
- Run the numbers before you buy. Whether pulling a deduction into this year actually helps depends on your income this year versus next year.
Timing expenses works best as part of a full plan, not as a last-minute reaction to a scary tax estimate.
What this looks like in practice
A social media influencer came to us in October. She was expecting a large balance due and had paid no estimated tax for the year.
We worked through all three moves together:
- We adjusted her S corp salary and made sure her withholding was enough to protect her against underpayment penalties.
- We set up her Solo 401(k) and funded a retirement contribution.
- We maximized her qualified business income (QBI) deduction through proper planning of her salary against her net profit.
- We moved a car purchase she was already planning into December.
Together, those changes lowered her federal and state tax by about $35,000 and eliminated thousands in underpayment penalties she would otherwise have paid.
None of these moves was exotic. What made them work was timing. She came in October, while every option was still available. If she had called in February, most of that savings would have been gone.
The two most common year-end mistakes
Mistake 1: Assuming the year can still be fixed later. This is the one we see most. Owners assume their accountant can work around anything at filing time. For most of the moves above, that simply isn’t true.
Mistake 2: Books that are months behind. Without current numbers, nobody can plan well, even in October. If your bookkeeping stopped in June, the first step is to catch it up, because every planning decision depends on knowing your actual profit for the year. Our small business accounting services exist so owners don’t land in this spot.
When to start the conversation
Technically, some year-end moves can still be made in the last week of December. In reality, setting up plans and making big purchases takes time to arrange and process, and accountants’ calendars fill quickly at the end of the year.
Iryna’s practical cutoff is the end of November. Clients who reach out by November 15 get a real planning conversation. After that, we still do what we can, but the options shrink every week.
“Once December 31 passes, the year is mostly locked. Payroll can’t be run retroactively. Plans that needed to exist by year-end can’t be backdated, and purchases can’t be moved into last year.”
Iryna Stepanchuk
If you’re reading this in late October, you are in a good position. Don’t panic about the balance you think you might owe. Use the next few weeks to get organized.
A simple year-end checklist
Before your planning meeting, gather:
- Year-to-date profit and loss and balance sheet, as current as possible
- Payroll reports, if you’re an S corporation owner
- Estimated tax payments made so far this year, federal and state
- Retirement plan details, or a note that you don’t have one yet
- Planned purchases for the next six months, with rough costs
- Major changes this year, such as a new entity, a big contract, or a new hire
With these in hand, a planning session can focus on decisions instead of digging for information.
Plan now, while you still have options
Year-end tax planning is not about finding loopholes. It’s about making the decisions you were going to make anyway, at the right time, with the tax consequences in view. We work with business owners across the United States, and the ones who save the most are almost always the ones who start early.
If you want a real planning conversation before the window closes, learn more about our tax planning services and reach out before November 15.
Frequently asked questions
What is the deadline for year-end tax planning for a small business?
For most planning moves, the deadline is December 31. Payroll, certain retirement plan setups, and purchases need to happen within the calendar year to count for that year. Practically, we recommend starting by mid-November, because plans and large purchases take time to arrange.
Can I still reduce my taxes after December 31?
A little, but not much. Some retirement contributions can be made up to the filing deadline, and your accountant can make sure everything is reported correctly. But most of the meaningful planning options close when the year ends.
Should I buy equipment before year-end to lower my taxes?
Only if your business already needs it. Buying and placing equipment in service before December 31 can move the deduction into the current year, but a deduction only reduces part of the cost. You still pay for the purchase, so it should make business sense on its own.
Why does S corporation payroll matter for year-end planning?
S corp owners who work in the business should pay themselves a reasonable salary through payroll. That salary affects your retirement contribution limits, your other deductions, and your exposure to penalties. Payroll can’t be run retroactively, so it has to be correct before the year ends.
What if my books are behind?
Catch them up first. Planning depends on knowing your actual profit for the year. Without current books, any year-end decision is a guess. The sooner your numbers are up to date, the more options you’ll have.
