Separate Two Kinds of Expenses First
Interiors work involves two very different expense buckets, and mixing them up is the most common source of confusion. There are client-billable expenses: furniture, fabric, fixtures, and materials you purchase on behalf of a project and either mark up or pass through on an invoice. Then there are business overhead expenses: software subscriptions, mileage, your studio rent, marketing, and continuing education. Only the second bucket reduces your taxable income as a deduction on Schedule C. The first bucket is really a pass-through cost of doing business, and it needs its own tracking so you can bill clients accurately and reconcile against vendor invoices.
A lot of designers use a dedicated business checking account and a business credit card just for procurement, which makes it much easier to separate client-reimbursable purchases from your own overhead at tax time.
Categorize As You Go, Not in April
Waiting until tax season to sort a year of Amazon, showroom, and vendor charges is how deductions get missed or misclassified. Set up categories that map to Schedule C: supplies, contract labor (for subcontracted drafters or stagers), advertising, car and truck expenses (mileage to job sites and showrooms), travel, and legal or professional services. Every time you make a purchase, snap a photo of the receipt and log which project or category it belongs to immediately. Bookkeeping software or even a well-maintained spreadsheet with a column for client name, project, category, and reimbursable status works, as long as you update it weekly rather than quarterly.
Mileage deserves its own log. If you drive to client homes, job sites, or vendor showrooms, track miles with a simple app or a notebook in the car. The IRS standard mileage rate changes each year, so check the current rate and multiply it by your business miles for a clean deduction.
Reconcile Monthly Against Bank and Card Statements
Once a month, pull your business bank and credit card statements and match every transaction to a category. This catches subscription charges you forgot about, duplicate vendor payments, and expenses you meant to bill a client but never invoiced. Monthly reconciliation also means you are never staring at twelve months of unsorted transactions in March.
If you take retainers or deposits before purchasing furniture and materials, keep a running list of what you have spent against each client deposit so you know exactly what is left to bill or refund. This protects you from accidentally spending client procurement money on your own overhead, which creates a mess when it is time to true up a project.
Save Every Receipt, Digitally
The IRS expects documentation for expenses you deduct, and paper receipts fade or get lost. Photograph or scan receipts the day you get them and store them by month and category, whether in cloud storage, email folders, or bookkeeping software. For expenses over 75 dollars there is generally an expectation of documentation, but keeping everything is safer and faster if you are ever asked to substantiate a deduction.
Set Aside Money for Taxes as You Invoice
Tracking expenses well also tells you your real profit, which matters because as a self-employed designer you owe self-employment tax of 15.3% on top of income tax, and you likely need to make quarterly estimated payments using Form 1040-ES. Knowing your true expenses each month means you know your true profit, and you can set aside the right percentage for taxes instead of guessing and getting hit with a bill you did not save for.