An ad hoc payment is a one-time financial disbursement a business makes outside its regular payment cycle to cover an immediate or unusual expense. Instead of running through standing payroll, automatic billing, or a recurring vendor schedule, each transaction is set up from scratch: recipient details entered, paperwork gathered, tax treatment decided, and payment method chosen for that single instance. The label covers a wide range of situations, from a performance bonus to an emergency plumber’s invoice, but the common thread is that the payment doesn’t fit any automated routine already in place.
Because these payments sit outside routine controls, the work of getting them right happens before and after the money moves. Beforehand: correct paperwork and proper tax withholding. Afterward: accurate recording and, where required, information reporting to the IRS.
When Businesses Make Ad Hoc Payments
Most ad hoc payments fall into a handful of recurring scenarios, even though each transaction is unique.
- Bonuses and commissions awarded outside the regular payroll run, triggered by a performance milestone rather than the calendar.
- Invoices from freelancers and independent contractors hired for a single project or a one-off emergency job.
- Urgent vendor payments when equipment breaks or a time-sensitive supply order comes in and the vendor isn’t set up in accounts payable.
- Employee expense reimbursements for business trips or client meals. Under federal rules, these stay tax-free only when the plan meets three conditions: the expense has a clear business purpose, the employee substantiates it with receipts within 60 days, and any advance exceeding actual costs is returned promptly. Miss any of those, and the reimbursement is treated as taxable wages.1eCFR. 26 CFR 1.62-2 – Reimbursements and Other Expense Allowance Arrangements
- Prizes, contest winnings, and referral awards paid to non-employees, which are reported on Form 1099-MISC when they total $600 or more in a calendar year.2Internal Revenue Service. About Form 1099-MISC, Miscellaneous Information
Classifying the payment correctly at the moment you make it prevents problems later. A bonus to an employee and a payment to a freelancer can look identical on a bank statement, but they follow entirely different tax and reporting paths.
Paperwork to Collect Before Sending Funds
Every ad hoc payment needs recipient identification, banking details, and a supporting document that justifies the amount. For domestic electronic transfers, that means the recipient’s full legal name, current mailing address, the bank’s nine-digit routing number, and the account number. Verify banking details through a second channel before sending: if a vendor emails new instructions, call the vendor at a number you already have on file to confirm.
For non-employees, collect a completed Form W-9 before releasing funds. The form captures the recipient’s legal name and Taxpayer Identification Number so you can file required information returns at year-end.3Internal Revenue Service. About Form W-9, Request for Taxpayer Identification Number and Certification If the recipient won’t provide a W-9 or gives an incorrect TIN, you’re required to withhold 24% of the payment as backup withholding and remit it to the IRS.4Internal Revenue Service. Instructions for the Requester of Form W-9 (03/2024)
For payments to foreign individuals or entities, W-9 doesn’t apply. Collect Form W-8BEN for individuals or W-8BEN-E for entities, whether or not a tax treaty reduces the withholding rate.5Internal Revenue Service. About Form W-8 BEN, Certificate of Foreign Status of Beneficial Owner for United States Tax Withholding and Reporting (Individuals)
Supporting documentation is the third piece. External payments should be backed by an invoice describing the goods or services and the agreed amount. Internal disbursements like bonuses should be backed by an authorization memo from the appropriate manager. Organized records protect the company during audits and simplify year-end filings.
Tax Withholding Depends on Who You’re Paying
Employees
When an ad hoc payment goes to an employee, the IRS treats it as supplemental wages. Bonuses, commissions, back pay, and severance all fall into this category, and the employer has two withholding options for federal income tax.6Internal Revenue Service. Publication 15 (2026), (Circular E), Employer’s Tax Guide
The flat rate method withholds 22% on supplemental wages up to $1 million paid to that employee during the calendar year. Once cumulative supplemental wages exceed $1 million, the excess is withheld at 37%. Most payroll systems default to this method because it’s simpler.
The aggregate method combines the ad hoc payment with the employee’s regular wages for that pay period, calculates withholding on the combined amount as though it were a single paycheck, then subtracts the tax already withheld from the regular wages. The remainder is the withholding attributed to the supplemental portion. Depending on the employee’s income level, this can produce more or less withholding than the flat rate.
Either way, standard Social Security and Medicare taxes still apply.
Independent Contractors and Freelancers
Payments to non-employees generally involve no upfront income tax withholding. The contractor handles their own estimated tax payments. The one exception is the 24% backup withholding that kicks in when the payee fails to furnish a valid TIN on Form W-9.4Internal Revenue Service. Instructions for the Requester of Form W-9 (03/2024)
Foreign Payees
Payments of U.S.-source income to a foreign person carry a default 30% federal withholding rate.7Internal Revenue Service. Tax Withholding Types If a tax treaty reduces or eliminates that rate, the reduction applies only when the payee has submitted a valid Form W-8BEN claiming the treaty benefit before payment.5Internal Revenue Service. About Form W-8 BEN, Certificate of Foreign Status of Beneficial Owner for United States Tax Withholding and Reporting (Individuals) Getting this wrong creates liability for the payer, not just the recipient.
How the Money Actually Moves
Once the paperwork is in order and withholding is calculated, the payment channel depends on urgency, amount, and destination.
ACH is the workhorse for domestic ad hoc payments. Standard ACH settles in one to two business days. Same Day ACH handles transactions up to $1 million and settles three times each business day, which covers most urgent domestic disbursements at a low per-transaction cost.8Nacha. Same Day ACH
Wire transfers provide same-day finality and are used when the amount exceeds ACH caps or when the recipient’s bank requires a wire. They cost more than ACH and are irrevocable once processed, so verification of recipient details matters even more than usual.
FedNow, the Federal Reserve’s instant payment service, settles in real time around the clock, including weekends and holidays, with individual transactions of up to $10 million.9Federal Reserve Financial Services. Customer Credit Transfer and Liquidity Management Transfer Network Limit Increases Not every bank participates, so confirm availability before relying on it for a time-sensitive payment.
Paper checks still have a role when the recipient can’t accept electronic transfers or internal policy requires them. They take longer and carry higher fraud risk because the account and routing numbers are printed on the check.
International transfers usually require a SWIFT code (or BIC) to identify the recipient’s bank and, in many countries, an IBAN to identify the account. Cross-border payments typically take two to five business days and can pick up intermediary bank fees along the way.
Recording and Year-End Reporting
Enter each ad hoc payment into the general ledger promptly and code it to the correct expense account. These payments are easy to lose track of precisely because they fall outside routine cycles, and one that sits in an uncategorized holding account will distort monthly reports.
If cumulative payments to a single non-employee reach $600 or more during the calendar year, you must file Form 1099-NEC reporting the total.10Internal Revenue Service. Instructions for Forms 1099-MISC and 1099-NEC (04/2025) – Specific Instructions for Form 1099-NEC The threshold is cumulative, so a $200 payment in March and a $450 payment in October together cross the line and trigger the filing requirement, even though neither payment alone would.
The filing deadline is January 31 of the year following payment, whether you file on paper or electronically,11Office of the Law Revision Counsel. 26 U.S. Code 6071 – Time for Filing Returns and Other Documents and a copy must be furnished to the recipient by that same date.10Internal Revenue Service. Instructions for Forms 1099-MISC and 1099-NEC (04/2025) – Specific Instructions for Form 1099-NEC The IRS applies per-return penalties that escalate the longer a filing is delayed, and those amounts multiply quickly across a company’s roster of contractors.12Internal Revenue Service. Information Return Penalties Collecting W-9s at the outset and tracking cumulative totals through the year is much cheaper than reconstructing them in January.
Fraud Risk on Non-Routine Payments
Ad hoc payments carry higher fraud risk than recurring ones because they lack a familiar pattern to compare against, and urgency often pressures staff to skip verification. Business email compromise is the most common threat: a fraudster impersonates a vendor or executive and requests an urgent payment or provides “updated” banking details. The FBI recommends verifying any change in payment instructions by calling the requester at a known number, not one supplied in the suspicious email.13Federal Bureau of Investigation. Business Email Compromise Legitimate vendors rarely demand same-day banking changes with no advance notice.
Dual authorization is the strongest internal control for these payments. One employee enters the transaction, a second independently verifies recipient information and releases funds. Most corporate banking platforms support this as a configurable feature, and enabling it above a set dollar threshold is one of the simpler security improvements a company can make.