Setting Aside Money for Taxes — A Seller's Guide

Every seller eventually hits the same surprise: money came in, fees were paid, inventory was bought, and then the tax bill arrives larger than expected. The problem is rarely that the tax was unfair — it is that the money wasn't set aside as it came in.

This guide covers the general concept of setting aside money for taxes. It does not tell you what your tax rate is. That number depends on where you live, how your business is structured, and how much you earn. What it does cover is a framework every seller can use to plan around their tax obligation.

Why sellers get surprised by tax bills

When you work for an employer, tax is usually withheld from each paycheck. Money that reaches your bank account has already had tax taken out — the bill is settled continuously, without the employee having to think about it.

Selling online works differently. When a customer pays, the full amount (minus platform fees) is treated as revenue to you. There is no withholding. If you don't actively set money aside, it gets spent on inventory, ads, or general expenses — and the tax obligation that comes due later has to be funded from whatever is left.

Three specific reasons online sellers get caught off guard:

• Revenue is not the tax base. The number shown under "sales" is revenue. What you owe is usually a percentage of net profit after deductible expenses. But without tracking those expenses, the revenue number can look like the taxable number — and the tax bill seems higher than expected.
• Fees are already gone. Platform fees and payment processing are deducted before the payout reaches you. If those are not counted as expenses, the taxable base is overstated.
• Inventory is not always an immediate expense. Depending on jurisdiction and accounting method, inventory may be treated as an asset until it sells — not as an expense at the moment of purchase. This can create a delay between when cash leaves and when the cost is deducted.

The set-aside concept

A set-aside is simple: every time you receive revenue, a portion of it is moved to a separate account before any of it is spent. That account exists for one purpose — paying the tax bill when it comes due.

The set-aside is not a legal requirement. It is a practical discipline that prevents the money from being spent on other things.

Common ways sellers manage this:

• Percentage on each payout. Every time a payout lands, a fixed percentage is transferred immediately to the set-aside account. Simple and automatic.
• Percentage on net profit. Instead of a percentage of gross revenue, the set-aside is calculated from net profit after platform fees and product cost. More accurate but requires tracking profit per period.
• Fixed monthly amount. A set dollar amount transferred each month, adjusted periodically based on sales volume. Less precise but easier to plan around.

The percentage method on gross revenue is the easiest to keep consistent because it happens on autopilot. The net profit method is more accurate because it reflects what you're actually earning. Either works if applied consistently.

Choosing a set-aside percentage

Different sellers use different percentages. There is no universal number — the correct one depends on jurisdiction, business structure, income level, and how much of your net profit is already deductible in your specific situation.

A general framework for thinking about it:

Many sellers start with a set-aside range based on their income bracket, then adjust after the first year once they see the actual tax bill. Starting conservative — closer to the higher end of the range — is almost always safer than starting optimistic and catching up later.

What counts as a business expense

Business expenses reduce the taxable base. Different jurisdictions have different rules for what qualifies and what does not, but most recognize some version of the same categories for online sellers. The list below is representative — confirm the specifics with a tax professional.

• Cost of goods sold. Product cost, inbound freight, duties, and inbound handling — usually treated under inventory accounting rules rather than as an immediate expense.
• Platform fees. Referral, transaction, and commission fees charged by the marketplace.
• Payment processing fees. Card processing, gateway fees, and any bank fees tied to receiving payments.
• Shipping and fulfillment. Outbound shipping, packaging supplies, fulfillment service costs.
• Advertising. Ad spend across any platform, ad creative production, and contractor costs for ad management.
• Software and subscriptions. Tools used to run the business — email, inventory, bookkeeping, design software.
• Home office. A portion of housing costs, in jurisdictions that allow it, if a space is used regularly and exclusively for business.
• Professional services. Accountant fees, legal fees, and consultant costs related to the business.
• Bank fees. Account fees and transaction fees tied to the business account.
• Samples and business travel. Where relevant to running the business and permitted by local rules.

The list is representative, not exhaustive. Each jurisdiction has its own specifics. What is deductible in one country may not be deductible in another, and the rules change periodically.

Why tracking expenses from day one matters

The reason to track expenses from day one is that most of them are easy to forget if they aren't captured when they happen.

Examples:

• A software subscription that seemed trivial in month one becomes a meaningful total by month twelve.
• Shipping costs accumulate across hundreds of small transactions — none memorable individually, but substantial in aggregate.
• Small home-office allocations are easy to overlook but legitimate when documented.

If tracking is deferred to the end of the year, most of these are lost. Even the ones that can be reconstructed from bank statements take hours to reconcile. Having a system in place from day one is a smaller task than rebuilding it later.

Simple tracking system

A basic setup that works for most small sellers:

• A dedicated business bank account. Every business transaction flows through one account, making categorization simple.
• A dedicated business card. Every business expense hits the card, generating a clean record automatically.
• A simple spreadsheet or bookkeeping app. Transaction date, amount, category, and note. Updated weekly, not monthly.
• A folder for receipts. Digital is fine. Photograph physical receipts when they arrive.
• A set-aside account. Separate from the operating account. Money transferred in regularly, moved out only when paying tax.

None of this requires expensive software or an accountant on retainer. The important thing is that the system exists before there is a backlog.

Periodic payments and deadlines

Many jurisdictions require sellers to pay estimated tax periodically through the year, rather than paying everything at the end. This applies to self-employed individuals and small businesses above certain income thresholds in many places.

Whether this applies to you depends on:

• Your jurisdiction (country and, if applicable, state or region)
• Your business structure
• Your income level
• Whether you have other sources of income with withholding

Missing periodic payment deadlines can result in penalties or interest in jurisdictions that require them. The specific schedule is set by each jurisdiction and can change.

Because this is highly jurisdiction-specific, it is one of the clearest reasons to have a local tax professional review your situation at least once. A one-time consultation at the start of the year often prevents surprises later.

A simple checklist for the first year

• Open a dedicated business bank account before your first sale.
• Open a separate set-aside account, physically distinct from the operating account.
• Decide on a set-aside percentage and apply it to every payout, without exception.
• Track every business expense in one place, updated weekly.
• Keep every receipt and statement for the retention period your jurisdiction requires — often three to seven years.
• Check with a local tax professional within the first three months of operation, even if only for a single session.
• Review the set-aside percentage quarterly. If sales volume has changed significantly, adjust.
• Before filing season, review the set-aside balance against the estimated liability. If there is a gap, address it in advance.

What to do next

If you are selling already, check whether a set-aside account exists. If it doesn't, open one and start funding it from the next payout. If a backlog of untracked expenses exists, work through the business bank statements and categorize them one month at a time until the backlog is cleared.

If you are about to start selling, set up the accounts and the tracking system before the first sale. Retroactive setup is possible but always harder.

The goal is not to avoid taxes. It is to make them a planned expense instead of a surprise.