Accountants do not want a shoebox, and they do not want forty emails either. They want a small number of complete, consistent files, delivered once, with a way to ask follow-up questions. Here is what that package looks like for a freelancer or a small single-owner business, and how to produce it without a last-minute scramble.
The core package
First, a full transaction ledger for the tax year: every income and expense entry with its date, vendor or payer, category, gross amount, business-use percentage, payment method, description, and whether a receipt is attached. A CSV file is the universal format; every accounting tool and spreadsheet opens it, and it survives being forwarded.
Second, expense totals by category. This is the summary your preparer maps onto the return, and having it pre-computed from the same ledger means the numbers reconcile by construction. Third, the receipts themselves, or read-only access to where they live, so individual entries can be verified without you playing go-between.
Add anything that lives outside your ledger: statements for business bank and credit card accounts, forms that report income paid to you, payroll summaries if you have employees or contractors, and records of equipment purchases with dates and costs.
Formatting that saves everyone time
Use plain dates in year-month-day order, amounts without currency symbols, and one row per transaction. Keep income and expenses in the same file with a type column rather than two files that have to be reconciled. Use the same category names all year; renaming categories in December creates reconciliation work for no benefit.
If a transaction was partly personal, show the gross amount and the business portion as separate columns rather than entering a reduced amount. Preparers need to see the whole picture to apply the right treatment, and a visible percentage is a defensible one.
Access instead of attachments
The most reliable handoff is read-only access to your bookkeeping workspace: the accountant sees the live ledger, downloads the exports and receipts they need, and never edits anything. You stay in control of the records and of who can see them, and you can revoke access when the engagement ends. Email attachments, by contrast, create copies you cannot recall and versions that drift apart.
Whatever you share, agree on the cutoff date first. Lock the year by marking entries reviewed, send the package once, and route any corrections through the ledger so the exports stay the source of truth.
Every preparer has preferences. Ask yours early in the year which files and formats they want, then set up your ledger to produce exactly that.