What Actually
Expires Early

Arc 5 opened on a single distinction: equipment must be placed in service, not merely ordered. This closes it with the rest of the list, because that distinction is not the only one with a calendar attached.

Sorted by when the option actually closes rather than by importance, because importance is not what makes something urgent. Several of these are worth doing regardless. What they have in common is that in December the choice has already been made for you.

Giving Changed This Year, and Timing Now Matters

The One Big Beautiful Bill Act rewrote the charitable contribution rules in Internal Revenue Code section 170, effective for tax years beginning after December 31, 2025. That means 2026 is the first year the new rules apply, and the returns reflecting them are filed in early 2027.

Two changes pull in opposite directions. For the roughly nine in ten taxpayers who take the standard deduction, there is now a deduction where previously there was none: up to $1,000 for a single filer and $2,000 for a married couple filing jointly, for cash gifts to qualifying public charities, taken above the line rather than as an itemized deduction. For itemizers, a new floor means only giving above 0.5% of adjusted gross income is deductible at all.

That floor is what turns giving into a timing question, because the floor applies per year. Give the same total across two years and you absorb it twice. Concentrate it into one year and you absorb it once.

For a small business owner this is a genuine September decision, because acting on it means either accelerating next year's giving into this December or deferring this year's into next January. Either way the charities you support deserve notice, and your own cash flow needs to accommodate a doubled year. Neither is a conversation to start on December 28.

The One That Cannot Be Fixed Retroactively

If you operate as an S corporation and take distributions, the reasonable compensation question is settled through payroll, and payroll is a thing that happens on dates. Wages paid in 2027 are 2027 wages. There is no mechanism for deciding in March that you meant to pay yourself a salary last year.

This is the item most likely to produce a genuinely expensive surprise, and it is entirely a scheduling problem. A corrective payroll run needs the payroll provider's processing calendar, the cash to fund the wages and the employer taxes, and the deposit made on schedule. December is a short month with holidays in it, and payroll providers publish cutoffs well before the 31st.

The Hour That Saves a Week in January

Every contractor you paid this year that requires a 1099 needs a taxpayer identification number, and the time to collect it is while they still want something from you. In January, a vendor you last worked with in March has no particular reason to return your call quickly.

Pull the vendor list now, identify who will need a form, and check whether you hold a current W-9 for each. Chasing three missing forms in September is an hour. Chasing them the week before the filing deadline is a different experience entirely, and the information returns are due early in the year.

The Whole List, Sorted by When It Closes

• Closed or closing Establishing a SIMPLE IRA for this year. The window ran to October 1, which is now two weeks out. If this was on your list, it is this week's decision or next year's.
• September or October Equipment and vehicles with any lead time. Placed in service by December 31 is the test, so delivery and installation have to fit inside the remaining calendar. Ordering is not the milestone.
• September or October Corrective S corporation payroll. As above. Spreading it across remaining periods is far more comfortable than a single December run, and it requires deciding while periods remain.
• September or October A charitable timing decision. Concentrating or deferring giving needs a conversation with the organizations involved and room in your cash plan for an uneven year.
• September or October Withholding adjustments, if you or a spouse have wage income. Covered last week: withholding is generally treated as paid evenly across the year, which makes it a useful late lever, but payroll changes need lead time to take effect.
• December is fine Purchases you can buy and use the same week. Software, small tools, supplies, anything without delivery or installation. Waiting is actively better here, because December decisions are made with more information.
• December is fine Paying deductible expenses already committed. On a cash basis, when the payment clears determines the year. That is a genuine December decision and it benefits from knowing how the year finished.
• December is fine Timing late-December invoicing. Whether work done in the last week is billed this year or next shifts income across the boundary, and the right answer depends on which year is higher. That is knowable in December and not before.

Running This in Practice

What Arc 5 Adds Up To

Four posts on a single idea: the distance between a decision and its deadline is the whole of tax planning. Equipment turns on being placed in service rather than purchased. A retirement plan turned on October 1. Payroll turns on dates that cannot be revisited. Charitable giving now turns on which side of December 31 a gift falls.

None of these are complicated once seen. All of them are invisible if the first time you think about the year is after it has ended. That is the difference between tax preparation and tax planning, and it is a difference measured in months rather than in expertise.

Friday, and What Follows

Digital Friday returns September 18. On the financial side, Arc 5 closes here, and the remaining weeks of the quarter turn to what a small business should have settled before the calendar year ends. If you take one thing from these four posts, make it the calendar entries: the list is short, and scheduling it is the part that actually changes outcomes.

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