My Biweekly Paycheck Calendar Said 26 Pay Periods. 2026 Has 27.

I was in the middle of reviewing Q1 budget numbers when our accountant, Maria, pinged me on Slack. "Hey — quick question. Does our payroll calendar account for the 53-week year in 2026?"

I stared at the message. 53-week year? I had never heard those words together before. I'd been running this startup's finance operations for two years and I couldn't tell you whether a year could have 53 weeks. I assumed 52 was a fixed number — like 12 months, 365 days. Fixed.

I was wrong. And that wrongness was about to cost us.

Biweekly means 26 paychecks. Except when it doesn't.

Here's the math I had in my head when I set up our payroll calendar in 2024:

52 weeks per year. Biweekly pay = every 2 weeks. 52 divided by 2 = 26 pay periods. Each employee gets 26 paychecks. Annual salary divided by 26 = per-paycheck amount. Simple.

I built our entire payroll schedule on that assumption. Two pay periods per month, with a couple of "three paycheck months" sprinkled in. The spreadsheet was clean, the formulas worked, and nobody complained for two years.

Then Maria sent me a Wikipedia link to ISO week date. I scrolled down to the section about "Weeks per year" and saw this line:

A year has 53 weeks if and only if it starts or ends with a Thursday (in the Gregorian calendar).

I opened my calendar. January 1, 2026 is a Thursday. My stomach dropped.

The $9,200 I didn't budget for

Let me explain why this matters with real numbers. Say you have an employee making $60,000 a year on biweekly pay. Most years, you calculate their per-paycheck amount as $60,000 / 26 = $2,307.69. Twenty-six checks, $60K total.

In a 53-week year, there are 27 biweekly pay periods. Not 26. And if your payroll calendar just blindly generates paychecks every two weeks, you're going to issue that 27th check — which means you're paying that employee $62,307.69 instead of $60,000.

For one employee, it's a $2,307 rounding error. For our team of 8 people, it's about $9,200 in unplanned payroll expense. That's a real chunk of runway for a startup.

But here's the thing I didn't realize until I dug deeper: the problem isn't always extra money going out. For companies that pay hourly, the problem is actually the opposite — the extra week means employees work more hours than the annual budget accounts for. If your hourly labor budget assumes 2,080 hours per person per year (52 weeks x 40 hours), a 53-week year gives you 2,120 hours. That's 40 unbudgeted hours per employee.

I called up a friend who runs a small manufacturing shop with 15 hourly workers. When I told him about the 53-week thing, he went quiet for a moment. Then he said: "So you're telling me I'm going to pay for 600 more hours of labor this year than I planned for?"

I didn't have a good answer.

Why payroll software doesn't always catch this

You'd think payroll software would handle this automatically. Some do. Gusto, for example, adjusts for 53-week years if you've configured your pay period correctly. But a lot of small businesses — and I was one of them — aren't using Gusto. They're running payroll from a Google Sheet, or a lightweight payroll tool, or QuickBooks with mostly default settings.

QuickBooks, ADP, and similar platforms can handle 53-week years, but they don't necessarily warn you about them. You have to know to look for it. The extra pay period just shows up in the calendar and if you're not paying attention — which I wasn't — you don't notice until the money's already out the door.

I spent an afternoon reviewing our payroll setup and found three different places where the 53-week assumption was missing:

• Our annual compensation budget spreadsheet divided everything by 26 — hardcoded
• Our cash flow projection assumed exactly 26 pay periods per fiscal year
• Our contractor agreements specified "26 biweekly payments" instead of "biweekly payments for the duration of the contract"

That third one was the one that actually worried me. We had written a contract with a contractor that explicitly said 26 payments. If they worked through the end of 2026, they were entitled to 27. The contract language was technically wrong, and while I doubted they'd sue us over one extra payment, it was a legal loose end I didn't want dangling.

Which years have 53 weeks?

After my panic-induced research session, I made myself a cheat sheet. A year has 53 ISO weeks when:

• The year starts on a Thursday (like 2026)
• Or the year is a leap year that starts on a Wednesday (like 2020 was)

This happens roughly every 5 to 6 years. Recent 53-week years: 2009, 2015, 2020, 2026. Next ones: 2032, 2037, 2043.

You can also just check weeknumber.cc and look at the full year calendar. If December 31 falls in Week 53, you have a 53-week year. It takes about 3 seconds to check.

I now do that check every October during budget season. It's the first thing I do, before I open any spreadsheet.

What you should do right now (like, today)

If you handle payroll or budgeting for a company — even a tiny one — here's what I'd suggest:

First, check if your payroll calendar has 26 or 27 pay periods for 2026. Don't assume. Open the actual calendar and count.

Second, if you have 27, decide how you're handling it. Options include: adjusting the per-paycheck amount so the annual total stays the same (for salaried employees), budgeting the extra period as a separate line item, or — and I learned this is a thing some companies do — skipping the last pay period and rolling it into the first one of the next year. That last one is messy and I don't recommend it, but it exists.

Third, talk to your accountant or whoever handles your financial projections. Make sure the extra pay period is reflected in cash flow forecasts. A surprise $9,200 in payroll is a lot easier to handle when you know it's coming six months in advance.

I caught our 53-week problem in March of 2026, which gave us most of the year to adjust. If I'd caught it in November, I would have had about 6 weeks to scramble. The earlier you check, the less painful it is.

Maria still jokes about it. "Remember when you didn't know years could have 53 weeks?" Yes, Maria. I remember every time I update the payroll calendar.