S corporation bookkeeping checklist: monthly, quarterly and year-end

Why S corporation books need more than a Schedule C ledger

As a sole proprietor, money moving between you and the business was mostly a draw, and the tax return did not care much how it was labeled. In an S corporation it matters. Salary is wages with payroll taxes. Distributions are payments to a shareholder and are not wages. A loan to or from the owner is neither. A reimbursement of a business expense the owner paid personally is something else again.

Each of those is reported differently on the S corporation return and the owner's return, and several of them affect the owner's basis in the company. Books that lump them together as "owner draws" leave the preparer to reconstruct the year, usually in March.

Accounts to set up once

• Officer wages, separate from other employees' wages
• Employer payroll taxes, including Massachusetts PFML and, if applicable, unemployment contributions
• Shareholder distributions, recorded in equity rather than as an expense
• Shareholder loans, as a receivable or payable, with a separate account for each owner
• Owner expense reimbursements under the accountable plan
• Health insurance premiums for shareholders owning more than 2%, kept separate so they can be added to the W-2
• Fixed assets, with enough detail to handle the federal and Massachusetts depreciation differences

If you converted from a sole proprietorship or single-member LLC mid-stream, the opening balances on the S election date deserve a proper cutoff. Transactions before and after that date go on different returns.

Every month

1. 1.Reconcile every bank, credit card and loan account to its statement.
2. 2.Record payroll from the provider's reports: gross officer wages, withholding, employer taxes and net pay, and confirm the deposits cleared.
3. 3.Code every transfer to the owner as salary, distribution, loan or reimbursement. Nothing stays in a suspense account at month-end.
4. 4.Process owner expense reports under the accountable plan and pay them as reimbursements, not as distributions.
5. 5.Attach or file receipts that identify the payee, amount, date, proof of payment and what the expense was for.
6. 6.Review the profit and loss and balance sheet for the month and year to date.

Distributions versus shareholder loans

A distribution is the owner taking profit out as a shareholder. A loan is money the owner or the company expects to be repaid. The distinction is not the label in the bank memo; it is whether there is a real obligation to repay. A loan that is never documented, never charged interest and never repaid tends to look like something else when the return is prepared.

The Form 1120-S instructions list repayment of loans from shareholders and distributions separately among the items affecting shareholder basis, which is a good reason to keep them in separate accounts from the start. If the owner does lend money to the company, a short written note of the amount, terms and repayment plan is worth the ten minutes it takes.

Reimbursements under an accountable plan

When the owner, as an employee of the S corporation, pays a business expense personally, the clean way to get the money back is a reimbursement under an accountable plan. IRS Publication 463 describes three rules for such a plan: the expenses must have a business connection, the employee must adequately account for them within a reasonable period, and any excess reimbursement must be returned within a reasonable period.

Reimbursements that meet those rules are not wages. Payments that do not meet them are treated differently, which is why the books should show an expense report and receipts behind every owner reimbursement, rather than round transfers labeled "expenses".

Every quarter

• Agree the payroll provider's quarterly reports to the officer wages and payroll tax accounts in the books.
• Confirm Massachusetts PFML contributions and, if the business is covered, the DUA wage report due 30 April, 31 July, 31 October or 31 January.
• Compare year-to-date owner salary with year-to-date distributions and ask whether the salary still reflects the owner's actual role.
• Review the owner's estimated tax position, since S corporation profit passes through to the personal return.
• Check the running shareholder loan balance and any repayments.
• Update the basis worksheet with the quarter's distributions and contributions.

Tracking basis

Each shareholder has a basis in their stock, and in any loans they have made to the company. In general terms, the IRS instructions describe basis being increased by income items and reduced by distributions and other items; the Form 1120-S has a whole group of lines headed "Items Affecting Shareholder Basis". Basis is what determines how distributions and losses are treated on the owner's return.

Basis is tracked by the shareholder, not by the corporation's return, and nobody can reconstruct it reliably years later without the records. A running worksheet updated at each year-end, starting from what the owner contributed when the S election took effect, is far cheaper than rebuilding it later.

Losses, distributions larger than the year's profit, and loans in either direction are the situations where basis stops being a formality. If any of them applies, raise it before year-end rather than at filing.

At year-end

• Reconcile December accounts and close the year in the books.
• Add health insurance premiums for more-than-2% shareholders to their W-2 Box 1 wages; they are not Social Security or Medicare wages.
• Tie total officer wages on the Forms W-2 to the officer wages account.
• Issue Forms 1099-NEC where required: the threshold is $600 for payments made in 2025 and $2,000 for payments made after 31 December 2025, with attorney payments still at $600.
• Update the fixed asset list; Massachusetts does not allow federal bonus depreciation and, for tax years 2025 and 2026, uses the section 179 limits without the 2025 federal increases.
• Finish the basis worksheet and document any shareholder loan balance.
• Assemble the trial balance and supporting schedules for Form 1120-S and Form 355S.

The returns the books feed, and when

The due dates below are the ones the year-end books have to be ready for.

The IRS says to keep employment tax records for at least 4 years after the tax is due or paid, whichever is later, and records connected to property until the limitation period expires for the year you dispose of it.

Where we come in

We keep monthly books for S corporations and prepare Form 1120-S and Form 355S from them, so the year-end steps above are part of the same work rather than a separate cleanup. If the books are behind, catch-up work comes first and is scoped separately. We give you a scope and a price in writing before anything starts.