Petty Cash: How to Set Up and Run a Fund for Your Business

Petty cash is a small amount of physical cash a business keeps on hand to pay for minor expenses that are awkward to put on a card: postage at the counter, a box of printer paper, coffee for a client meeting. The IRS describes it plainly in Publication 583: "A petty cash fund allows you to make small payments without having to write checks for small amounts." The catch is that a drawer of loose bills becomes a liability the moment it goes untracked. Run as a disciplined system, petty cash gives you clean, deductible records for every small purchase. Run as a "grab a twenty when you need it" habit, it quietly erases deductions and throws your books off. This guide walks the system that keeps it the first kind.

What is petty cash?

Petty cash is a fixed sum of cash, kept in a locked box or drawer, that a business spends down on small purchases and then tops back up. It is not the owner's wallet and it is not a slush fund. It is an asset account on your books, usually called Petty Cash, that starts at a set amount (the "float") and is supposed to always equal the same total when you add up the cash still in the box plus the receipts for everything spent out of it.

The reason to keep one at all is narrow but real. Most business spending today runs through a card or a bank transfer, which leaves an automatic trail. A few purchases still don't: a $6 parking fee, stamps at the post office, a cash-only farmers-market supplier. For those, petty cash beats putting the owner's personal cash in and forgetting to log it, which is how small deductions disappear.

The imprest system: how a petty cash fund works

The standard way to run petty cash is the imprest system. "Imprest" means the fund is fixed at a set amount and restored to that exact amount each time you refill it. The mechanics are simple:

1. You set a float, say $200, and move that cash from your checking account into the box.
2. Every time someone spends from the box, they drop a slip and the receipt back in, so the box always holds cash plus paper that adds up to $200.
3. When the cash runs low, you write one check (or one transfer) for exactly the total spent, which brings the box back to $200.

The elegance is the constant total. At any moment, cash on hand plus the receipts in the box should equal the float. If it doesn't, you know immediately that something is missing, and you know exactly how much. That built-in check is why the imprest system, rather than a free-floating cash pile, is the version worth running.

Under an imprest fund, the float itself is never an expense. Moving $200 from checking to the box just relocates cash from one asset account to another. The expenses land on your books later, at replenishment, when you sort the slips into categories. This is the single most misunderstood point about petty cash, and the rest of the system depends on getting it right.

Setting up your petty cash fund

Standing up a fund takes four decisions.

Pick the float. Size it to about a month of small cash spending, not more. A solo consultant might need $100; a small studio with walk-in supply runs might want $300. Too large and you are holding idle cash that should be earning or working; too small and you are refilling constantly. Most one-person and small businesses land between $100 and $300.

Move the cash and record it. Write a check to "Petty Cash" or withdraw the float, and record the entry as a transfer from your bank account to the Petty Cash asset account. No expense is recorded yet. This keeps your chart of accounts accurate: total cash across bank plus petty cash is unchanged.

Name a custodian. One person owns the box, the key, and the log. In a solo business that is you. The point of a single custodian is accountability: when the fund is short, there is one person who knows what happened, not a committee.

Set the rules in one line. Decide the ceiling for a single payment (often $50), what the fund may be used for (business purchases only), and the non-negotiable rule that every disbursement gets a receipt. Written down, these rules are what separate a fund from a drawer.

Logging every disbursement with a petty cash slip

Every time cash leaves the box, two pieces of paper go back in: the vendor receipt and a petty cash slip. The slip is the IRS's own recommendation. Publication 583 says: "Each time you make a payment from this fund, you should make out a petty cash slip and attach it to your receipt as proof of payment." The IRS lists "petty cash slips for small cash payments" among the supporting documents a business should keep.

A slip is nothing fancy: date, amount, what it was for, who took the cash, and the expense category. It exists to capture the two things a bare receipt often doesn't, the business purpose and the category, so that at replenishment you are sorting, not reconstructing.

The receipt matters just as much as the slip, because proof of payment alone is not proof of a deduction. The IRS is explicit that supporting documents for an expense must "identify the payee, the amount paid, proof of payment, the date incurred, and include a description of the item purchased or service received that shows the amount was for a business expense" (IRS, What kind of records should I keep). A cash purchase with no receipt is a deduction you may lose in an audit, which is exactly the exposure petty cash is supposed to prevent. If no receipt is available, the slip with a full description is your fallback, and it should be the exception, not the routine. The same IRS receipt rules that apply to card spending apply to cash.

Reconciling the petty cash fund

Reconciliation is where the imprest system earns its keep. On a set schedule, monthly for most small businesses, or whenever the cash runs low, you count the fund and prove it back to the float.

Take a small print-and-design studio running a $200 float. Over the month, five payments came out of the box:

The receipts in the box total $112.50, so the cash still in the drawer should be $200 − $112.50 = $87.50. The custodian counts the bills and coins: if it comes to $87.50, the fund reconciles. Cash on hand ($87.50) plus receipts ($112.50) equals the $200 float, and the books are clean.

When the count doesn't match, the difference is real and you record it rather than fudge it. If the drawer held $85.50, a dollar short of the expected $87.50, you post the $2.00 gap to a Cash Over and Short account. Small shortages happen (a missing slip, wrong change) and the point of the account is to surface them, not hide them. A pattern of shortages is a signal to tighten the rules or the custodian, not to raise the float.

This is the same discipline as a bank reconciliation, scaled down to a cash box: you are proving a balance against independent evidence, and any unexplained difference is information.

Replenishing the fund and posting to Schedule C

Reconciliation tells you the fund is honest. Replenishment is where the month's small purchases finally become deductions. You write one check for the total spent, $112.50, which restores the box to $200, and you post that check split across the expense categories from the slips.

For a sole proprietor, those categories map straight to Schedule C lines:

The split adds up to the check exactly, which is the second built-in check of the system: if your categorized slips don't total the replenishment amount, a slip is missing or miscoded. One caveat on the meals line: business meals are generally 50% deductible, and the same business-purpose and receipt substantiation applies to a $24 coffee run from petty cash as to any other meal, so keep the who-and-why on the slip.

Notice what did and didn't hit the books. The $200 you put in at setup was never an expense. The $112.50 of actual purchases became expenses only now, at replenishment, sorted onto their proper lines. Petty cash isn't a cost; it's a holding tank, and only what flows out of it and gets replaced is deductible.

How SparkReceipt fits

The weak point of any petty cash system is the paper. Slips get lost, thermal receipts fade, and the shoebox reconstruction at month-end is exactly the job the fund was supposed to avoid. Capturing each slip the moment cash leaves the box fixes that. Snap the receipt with an AI receipt scanner, and the vendor, amount, date, and category are extracted and stored before the paper can fade. By replenishment time your expense tracker already holds every small cash purchase, categorized, so the split that posts to your books is a total you read off rather than rebuild. The cash box stays physical; the record of it doesn't have to.

Common petty cash mistakes

"The float is a business expense." Setting up a $200 fund records no expense at all. It moves cash from your bank to your petty cash account, both assets. Only the disbursements, booked at replenishment, are expenses. Treat the float as a cost and you will double-count when you refill.

"It's fine to borrow from petty cash." The moment the owner takes $40 for a personal lunch and means to pay it back, the fund stops reconciling and the box no longer holds cash-plus-receipts equal to the float. Petty cash is for business purchases with a receipt, full stop. Personal draws belong in an owner's draw, not the cash box.

"No receipt, no problem, it's only a few dollars." A cash purchase with no supporting document is the deduction most likely to be disallowed, because there is nothing to show the payee, amount, or business purpose the IRS asks for. The dollars are small individually, but a year of undocumented cash spending adds up to a real number you can't defend. The slip plus the receipt is the whole point.

Frequently asked questions

What is petty cash used for? Small business purchases that are impractical to pay by card or check: postage, parking, minor supplies, a cash-only vendor. The IRS frames it as a way "to make small payments without having to write checks for small amounts."

How much should a petty cash fund be? Enough to cover about a month of small cash purchases, commonly $100 to $300 for a one-person or small business. Size it to real spending so you are neither refilling constantly nor holding idle cash.

Is petty cash an asset or an expense? It is an asset. The fund sits on your books as a Petty Cash asset account. The float is never an expense; only the purchases paid out of it are, and they are recorded when you replenish the fund.

What is a petty cash slip? A short record of one disbursement, showing the date, amount, purpose, and category, attached to the vendor receipt. IRS Publication 583 recommends making one out for each payment as proof of payment.

How do I record petty cash on Schedule C? You don't record the fund itself. At replenishment, split the total spent across the Schedule C expense lines the slips fall under, for example office expense (line 18), supplies (line 22), or deductible meals (line 24b). The split should equal the replenishment amount.

Key takeaways

• Petty cash is a fixed float, not a slush fund. Run it on the imprest system: a set amount, spent down against slips and receipts, then restored to the same amount.
• The float is an asset, not an expense. Setting up the fund just moves cash between accounts. Only the disbursements become deductions, and only at replenishment.
• Every payment gets a slip and a receipt. The IRS recommends a petty cash slip per payment, and the receipt is what proves the payee, amount, and business purpose behind the deduction.
• Reconcile by proving cash plus receipts back to the float. Any difference goes to a Cash Over and Short account, surfaced rather than hidden.
• Replenish with one categorized check. The split posts to your Schedule C expense lines and must total the check, a built-in check that catches a missing slip.

A petty cash system is only as good as the slips behind it, and slips are the easiest paper in a business to lose. Capture each one as the cash leaves the box, categorize it once, and the month-end reconciliation and posting become a two-minute check. Get Started with SparkReceipt to keep every small cash purchase logged and categorized from the moment you make it.