Year-end tax planning works best when it starts well before clients start asking about it. For CPA firms, the weeks between Labor Day and December 31 are the last real window to influence a client’s tax outcome for the year, not just report it after the fact in April. The rules have also shifted meaningfully since last season.Â
The One Big Beautiful Bill Act (OBBBA) reset depreciation limits, retirement contribution caps rose again for 2026, and the SALT deduction cap moved higher too. A year-end tax planning strategies conversation built on last year’s numbers will steer clients wrong on more than one front this time around.Â
This piece walks through the year-end tax strategies worth raising with clients now, what changed under OBBBA that actually matters for 2026, and how to build a repeatable year-end tax planning for businesses checklist your firm can run every fall instead of rebuilding it from scratch.Â
Why year-end planning carries more weight this season?
Every filing season rewards firms that planned ahead over firms that filed reactively. This year, that gap is wider than usual.Â
Retirement contribution limits increased again for 2026. The IRS raised the 401(k) elective deferral limit to $24,500 and the IRA limit to $7,500, with a $8,000 catch-up for savers 50 and older and an $11,250 “super catch-up” for those aged 60 to 63, according to the IRS’s official 2026 cost-of-living adjustments. Clients who assume last year’s limits still apply are leaving money on the table, or worse, over-contributing.Â
Standard mileage deductions changed mid-year too. The IRS set the 2026 business mileage rate at 72.5 cents per mile in January, then raised it to 76 cents per mile effective July 1, 2026, citing rising vehicle operating costs. Any client tracking mileage manually needs to split their log at that date, not apply one flat rate to the full year.Â
What OBBBA changed for 2026 business filers?
Most of the year-end conversation this season runs through the OBBBA provisions that took effect in 2025 and adjusted again for 2026, like:Â
- Bonus depreciation is back at 100% permanently: OBBBA restored full first-year bonus depreciation for qualifying property placed in service after January 19, 2025, reversing the phase-down that was set to hit 20 percent in 2026 and zero in 2027. For clients weighing an equipment purchase before year-end, this is the single biggest lever available.Â
- Section 179 expensing limits also increased: For 2026, the Section 179 deduction cap is $2.56 million, with a dollar-for-dollar phase-out starting once qualifying purchases exceed $4.09 million, per IRS Revenue Procedure 2025-32. Most small and mid-sized clients will never approach the phase-out, which makes the deduction close to unlimited in practice for them.Â
- The SALT deduction cap moved again too: OBBBA raised the cap from $10,000 to $40,000 for 2025, and it rises 1 percent annually through 2029 before reverting to $10,000 in 2030. For 2026, that puts the cap at $40,400. High earners still face a phase-out above $500,000 in modified adjusted gross income, so the benefit isn’t universal, but it changes the itemize-versus-standard-deduction math for a lot of clients who assumed the old $10,000 cap still applied.Â
Firms whose PTET election workflow hasn’t been touched since 2023 should revisit it now. The pass-through entity tax workaround still stands, and OBBBA didn’t restrict it, but the math behind whether it’s still worth electing has shifted for clients now benefiting from the higher SALT cap.Â
Year-End tax planning strategies to walk clients through before December 31
These are the moves worth raising in a year-end client conversation, in roughly the order they tend to matter most:Â
- Max out retirement contributions before the deadline: Employer-sponsored plan contributions need to be made by December 31 to count for 2026, while IRA contributions have until the following April. Flag the new $24,500 401(k) limit and the $11,250 super catch-up for clients aged 60 to 63 specifically, since that’s an easy one to undersell.
- Time equipment purchases to capture bonus depreciation: With 100% bonus depreciation permanent under OBBBA, a client planning a capital purchase in Q1 next year may do better buying and placing the asset in service before December 31 instead. This is one of the clearer year-end business tax planning conversations to have, because the number is concrete and the deadline is fixed.
- Revisit the PTET election before it’s too late to act: Most states require the pass-through entity tax election, or the estimated payment that supports it, before year-end. Given how the higher SALT cap interacts with PTET benefits differently than it did in 2024, this isn’t a rubber-stamp renewal this year.
- Match income and expense timing to the client’s bracket: Deferring December invoices into January, or accelerating deductible expenses into the current year, still works, but only after checking whether OBBBA’s changes to bonus depreciation or QBI thresholds shift which year is actually cheaper.
- Bunch charitable contributions where it helps: Clients close to the standard deduction threshold may benefit from concentrating two years of giving into one, especially combined with the new above-the-line charitable deduction of up to $1,000 ($2,000 for joint filers) available to non-itemizers starting in 2026.
- Reconcile mileage logs against the mid-year rate change: Any client using the standard mileage method needs their log split at July 1, 2026, to reflect the move from 72.5 to 76 cents per mile. A single blended rate applied to the full year will misstate the deduction.
- Evaluate a Roth conversion window: For clients expecting a lower-income year or anticipating higher future rates, converting traditional IRA funds before year-end can lock in today’s tax rate on the converted amount. This is one of the more client-specific end of year tax strategies on this list and needs an actual projection, not a rule of thumb.
Most of these apply broadly, but a few are squarely small business end of year tax tips rather than individual moves, particularly the equipment timing and PTET election points. Flag that distinction early in the client conversation so the meeting doesn’t run long explaining strategies that don’t apply to them.Â
Building a repeatable year-end planning process for your firm
The strategies above only help clients if the firm has bandwidth to walk through them individually before December 31, and that’s usually where the process breaks down, not the tax knowledge.Â
A short internal checklist helps more than a long one. Flag every client with a pending equipment purchase, every S-corp or partnership eligible for a PTET election, and every client near a retirement contribution deadline, then batch those conversations into focused blocks rather than working through the client list alphabetically.Â
Firms running lean staff during this stretch often lean on outsourced tax preparation support to handle the return-level workpapers while partners focus on the planning conversations that actually need a CPA’s judgment. That split, planning work staying internal and compliance-heavy prep work getting outsourced, tends to be where firms find the extra capacity this time of year actually requires.Â
Conclusion
Year-end planning only pays off when it happens ahead of the deadline. Bonus depreciation, the Section 179 cap, the SALT deduction increase, and the new retirement limits all reward firms that get in front of client conversations in October and November, well before the March scramble leaves no room to act on any of it.Â
The bigger constraint for most firms isn’t tax knowledge, it’s bandwidth. Partners who understand every OBBBA change still can’t run forty individual planning conversations if the team is buried finishing return-level workpapers from the last engagement. That’s usually where the checklist above stalls out in practice, not at the strategy stage.Â
Datamatics Business Solutions works with CPA firms on exactly this kind of seasonal capacity, handling compliance-heavy prep work so partners can stay focused on the planning conversations that need their judgment. If your firm needs that extra room this season, book a call with our team and we’ll walk through what support looks like for a firm your size.Â
What's the deadline for year-end tax planning moves?
Most moves, including retirement contributions to employer plans, equipment purchases for bonus depreciation, and PTET elections, must be completed by December 31, 2026, to count for that tax year.Â
What changed under OBBBA for 2026 business tax planning?
Bonus depreciation is permanently restored to 100 percent, the Section 179 cap rose to $2.56 million, and the SALT deduction cap increased to $40,400, up from the pre-OBBBA $10,000 limit.
Should every client still make a PTET election?
Not automatically. The higher SALT cap changes the math for some clients, so firms should re-run the comparison rather than renewing last year’s election by default.
Why does the mileage rate change matter for year-end planning?
The IRS raised the 2026 business mileage rate mid-year, from 72.5 to 76 cents per mile starting July 1. Clients need to split their mileage logs at that date to claim the correct deduction.
How can firms handle year-end planning without falling behind on other work?
Many firms outsource return-level prep and bookkeeping during this stretch so partners can focus on client-facing planning conversations instead of splitting attention across both.Â
