When most people think about taxes, they think about April 15. But for business owners, some of the most important tax decisions need to happen months before the tax return is ever filed.

In fact, if you are waiting until your CPA prepares your return in February, March, or April to start thinking about tax savings, you may have already missed some of your best opportunities. Tax preparation tells you what happened. Tax planning gives you an opportunity to make informed decisions before the year is over.

As the fourth quarter approaches, business owners have a limited window to review their financial position, project their tax liability, and take legitimate steps that could potentially reduce their tax burden. For many strategies, December 31 is the critical deadline.

Why Q4 Tax Planning Matters for Business Owners

Running a business means making decisions every day. You monitor revenue, expenses, payroll, hiring, marketing, cash flow, and growth. Taxes should be treated with the same level of attention.

Unfortunately, many business owners treat taxes as something that happens after the year is finished. They hand their books to their CPA during tax season, receive a number showing what they owe, and then wonder what they could have done differently.

By that point, many opportunities have already passed.

You generally cannot wait until the following year and simply decide that a purchase, retirement contribution, income-timing decision, or other strategy should have applied to the previous tax year. The exact rules vary by strategy, but the underlying principle is simple: effective year-end tax planning happens before the year closes.

That is why the fourth quarter is such an important time for business owners. You still have enough information to make realistic decisions, while there may still be enough time to act.

1. Run a Tax Projection Before the Year Ends

The first step in effective Q4 tax planning for business owners is knowing where you actually stand.

A tax projection estimates your expected taxable income and tax liability based on what your business has already earned, what you expect to earn during the remainder of the year, anticipated expenses, retirement contributions, deductions, and other relevant factors.

Without a tax projection, you are essentially making tax decisions in the dark.

You may know that your business is having a great year, but you may not realize how much your increased income could change your tax liability. A projection gives you a clearer picture of what happens if you make no changes and helps identify areas where legitimate planning opportunities may still exist.

For example, imagine a consultant who is on track to generate approximately $320,000 in net business income. If that business owner waits until tax season to look at the numbers, there may be very few meaningful decisions left to make for the previous year.

If the same projection is completed in September or October, however, the business owner has time to evaluate retirement contributions, planned purchases, reimbursements, estimated tax payments, and other potential strategies.

The goal of a tax projection is not simply to find out what you owe. It is to understand your financial position while you still have time to make informed decisions.

If you have not completed a tax projection for the current year, talk to your CPA or tax professional now rather than waiting for tax filing season.

2. Review Your Retirement Plan Options

Retirement planning can be another important part of year-end tax planning, particularly for business owners who have significant income.

Many business owners are familiar with SEP IRAs because they can be relatively straightforward to establish and use. However, depending on your circumstances, a Solo 401(k) may provide different contribution opportunities.

The right choice depends on several factors, including your business structure, employees, compensation, age, existing retirement accounts, and whether you are interested in traditional or Roth contributions.

One important point is that retirement plan deadlines are not all the same.

For certain business owners, establishing a Solo 401(k) before the end of the year can preserve options that may otherwise be unavailable. There are also special rules that can apply to certain first-year plans for eligible sole proprietors without employees, which can affect when the plan may be established and when contributions can be made.

SEP IRA rules can provide additional flexibility because eligible contributions may generally be made by the business’s tax return deadline, including extensions, depending on the circumstances.

That does not mean a Solo 401(k) is always better than a SEP IRA, or vice versa. It means business owners should compare their options before the year ends instead of assuming that the simplest plan is automatically the best fit.

Your contribution limits, deadlines, eligibility, and tax treatment can vary significantly based on your situation, so this is an area where personalized professional advice is important.

3. Review the Timing of Income and Business Expenses

The third area to review is the timing of income and expenses.

For businesses using the cash method of accounting, there may be legitimate opportunities to influence when certain income and expenses are recognized. However, these decisions need to follow applicable tax rules and cannot be used to artificially manipulate income.

For example, if your business is having an unusually strong year and you reasonably expect the following year to be significantly lower, your tax professional may evaluate whether certain income can legitimately be deferred into the following year.

The opposite can also apply to expenses.

If you already know that your business needs new computers, equipment, technology, machinery, or other qualifying property, you may want to evaluate whether purchasing and placing that property in service before December 31 makes sense.

Section 179 may allow eligible businesses to deduct the cost of qualifying property placed in service during the tax year, subject to applicable limits and requirements.

The phrase “placed in service” is important. Simply ordering equipment does not necessarily mean it qualifies for a current-year deduction. The property generally needs to meet the applicable requirements and be placed in service during the relevant tax year.

Vehicles can involve additional rules and limitations, so they should be evaluated separately before making a purchase.

Most importantly, don’t buy something you don’t need simply because someone told you it will create a tax deduction.

Spending $50,000 to save a fraction of that amount in taxes is not automatically a smart financial decision. Tax planning should help you make better decisions about expenses you actually need, not encourage unnecessary spending.

If you were already planning to make a business purchase, however, the timing of that purchase may be worth discussing with your tax professional.

4. Clean Up Your Accountable Plan and Business Reimbursements

Business reimbursements are another area that can easily get overlooked during the year.

This is particularly relevant for S corporation owners and other business structures where an owner may personally pay for legitimate business expenses.

An Accountable Plan can allow an eligible business to reimburse employees for qualifying business expenses when the applicable IRS requirements are satisfied.

Depending on the circumstances, qualifying expenses can include business mileage, business travel, certain home office expenses, and business use of a personal phone or internet connection.

Proper documentation is critical.

Expenses generally need to have a legitimate business connection, be appropriately substantiated, and satisfy the applicable reimbursement requirements. When those requirements are met, qualifying reimbursements can generally be deductible to the business without being treated as additional taxable wages to the employee.

The IRS does not simply require every reimbursement to occur on December 31. The rules generally provide reasonable periods for substantiating expenses and handling excess reimbursements, including specific safe-harbor concepts.

Even so, reviewing your Accountable Plan during Q4 can make your bookkeeping, payroll treatment, and year-end tax reporting significantly cleaner.

If you operate an S corporation, ask yourself whether you have a written Accountable Plan and whether you have properly documented the business expenses you personally paid throughout the year.

This is also a good time to review other owner-related benefits, including health insurance, HSA contributions, and other benefits that may have their own eligibility and reporting requirements.

And remember, an Accountable Plan is not a replacement for reasonable compensation. S corporation owners still need to comply with applicable reasonable compensation requirements.

5. Review Your Estimated Tax Payments

By the fourth quarter, you should have a much clearer picture of your business’s performance than you did at the beginning of the year.

That makes this a good time to review your estimated tax payments.

If your income increased significantly, your original estimated payments may no longer reflect your current tax liability. Your CPA can compare your projected tax liability with what you have already paid and determine whether adjustments may be appropriate.

One concept that is particularly important is the estimated tax safe harbor.

Depending on your circumstances, paying enough through withholding and estimated payments to satisfy an applicable safe-harbor rule can help protect you from an underpayment penalty.

For many taxpayers, the general federal thresholds involve paying at least 90% of the current year’s tax or 100% of the prior year’s tax. Certain higher-income taxpayers may need to use 110% of the prior year’s tax for the prior-year safe harbor.

However, avoiding an underpayment penalty and avoiding a large tax balance are two completely different things.

You could satisfy an applicable safe harbor and still owe a substantial amount when you file your return because your business income increased significantly.

That is why your Q4 tax review should answer two questions.

First, are you on track to satisfy the applicable estimated tax requirements?

Second, based on your current projection, how much cash might you actually need when the tax return is filed?

Those numbers are not necessarily the same.

The fourth-quarter estimated tax payment is generally due January 15 of the following year. However, making a large payment in January does not automatically eliminate an underpayment from an earlier period. Estimated taxes generally operate on a pay-as-you-go basis.

If your income is uneven throughout the year, an annualized income installment method may also be relevant in certain situations.

Don’t Overlook Year-End Deductions and Investment Planning

Your Q4 tax review should not stop with business expenses and estimated payments.

If you are close to the threshold where itemizing deductions makes sense, charitable giving may deserve a closer look. Some taxpayers may benefit from strategically bunching charitable contributions into a particular tax year. A donor-advised fund can be one tool used for this purpose, depending on the individual’s circumstances and charitable goals.

Investment gains and losses can also be reviewed before the end of the calendar year.

If you have realized capital gains during the year, you may want to look at your investment portfolio for eligible positions that have declined in value. Tax-loss harvesting can potentially allow certain capital losses to offset capital gains, subject to applicable tax rules and limitations.

The important thing is to review these opportunities before December 31 rather than waiting until tax filing season.

Once the year has closed, some of these decisions can no longer be made for that tax year.

Why You Shouldn’t Wait Until April to Start Tax Planning

There is a major difference between tax preparation and tax planning.

Tax preparation looks backward. Tax planning looks forward.

When your CPA prepares your tax return, they are primarily documenting and reporting transactions that have already occurred. They can identify deductions and credits you qualify for and ensure the return is prepared correctly, but they cannot go back in time and change every decision you made during the previous year.

That is why waiting until February, March, or April to think about tax strategy can limit your options.

You cannot generally purchase equipment in February and decide that it should have been a December purchase. You cannot retroactively change when income was received simply because the tax result would have been better. And different retirement plans have different establishment and contribution deadlines.

The exact rules depend on your circumstances, but the principle remains the same: the earlier you start tax planning, the more information and flexibility you may have.

Your Q4 Tax Planning Checklist

As the year approaches its final quarter, business owners should review their tax position rather than simply wait for tax season.

Start with a current tax projection. Then review retirement plan options and deadlines. Look at the timing of income and business expenses. Review your Accountable Plan and outstanding reimbursements. Finally, compare your estimated tax payments with your projected liability and review any other year-end opportunities that may apply to you.

You do not need to implement every tax strategy you hear about.

The objective is to identify the strategies that actually make sense for your business and financial situation.

Start Your Year-End Tax Planning Now

For business owners, April 15 is an important tax deadline, but it should not be the date when tax planning begins.

The final months of the year can provide an important opportunity to understand your projected tax liability, review your options, and make informed financial decisions while there is still time to act.

A tax projection can tell you what your current situation looks like. A thoughtful Q4 tax planning process can help you determine what decisions are worth considering before the year closes.

So don’t wait until your CPA asks for your tax documents next spring.

Start the conversation now.

Review your numbers. Understand your projected tax liability. Evaluate your retirement plan. Review your expenses and reimbursements. Check your estimated payments. And make sure you understand the deadlines that apply to your specific situation.

Because tax preparation tells you what happened.

Tax planning gives you time to make informed decisions about what happens next.