Business Tax Deadline, the S corporation Monday

An S corporation on a calendar year files Form 1120-S on the 15th day of the third month. In 2026 that is Monday 16 March, the same Monday a partnership uses. The forms are not the same. The pressure feels the same, because the owner's personal return is stuck until the K-1 exists. A shareholder who keeps asking for that K-1 in February is asking for a number the company month has not earned yet. We would rather show an open February than invent the line that will land on the form.

Owners who were paid wages through the year sometimes think the W-2 finished the company. It did not. The W-2 is the wage. The K-1 is the rest of the company. Both have to be true before the personal return is honest.

IRS Publication 509 is the table for the weekend rule. A due day that lands on a weekend moves to the next business day.

If people are paid through this company, the payroll file can be set up here. The provider you already trust runs payday, the deposits, and Form 941. We do not take that run over. Mixing the wage dates into the March Monday is how a deposit gets called the company tax day.

The same week a payroll might run is the week the shop stays open after the door is locked and the back room is the only light left. We know that week. The lights do not file the wage report. The provider does, on the schedule you already have, and we only set the payroll file up.

By the time March arrives, the year is over and the Monday is a filing day. The decisions that change the year belong earlier. October is when we sit down with the still-open year, while owner pay and an estimate can still be moved. The Monday itself will not move.

The 1120-S is assembled only after each month's bank already agrees, beginning with the February that sits under that Monday. We do not represent you before the IRS. A lender who wants a signed report is pointed to a firm that can sign one.