The year-end pain most trades feel is not the tax return: it is rebuilding a year of invoices from bank statements, van folders and memory. A clean CSV export of your invoices turns that into an afternoon. This guide covers what your accountant actually needs, how to export it, and the monthly habit that keeps year end boring.
- Your accountant needs a dated, numbered invoice list, not bank statements.
- Export monthly, not annually; the year-end job is then a merge, not an excavation.
- Include CIS deductions and VAT columns or they get reconstructed at cost.
- Keep numbering continuous and records for years after the tax year.
- Clean CSVs cut accountancy fees. You stop paying for admin time.
What your accountant actually needs
Everything your accountant does for the year flows from the same inputs. For a typical sole-trader or small-company trade business, that is:
| What | Why | Where it comes from |
|---|---|---|
| All invoices issued (number, date, client, amount, VAT) | Turnover and the sales side of accounts | Invoicing software export |
| All CIS deductions suffered | Offset against your tax bill | Contractor statements / your invoices |
| Business expenses | Deducted from profit | Receipts, statements, your records |
| Bank statements | Reconcile everything | Bank |
| VAT records (if registered) | VAT return support | Your software’s VAT report |
The first row is the one most trades fail at, because invoices live in a dozen formats. A CSV export solves it: which is why the export feature matters more than most when choosing invoicing software.
The monthly export habit
The workflow that makes year end trivial takes ten minutes a month:
- On the last working day of each month, export invoices issued that month as CSV: number, date, customer, description, net, VAT, gross, status, amount paid, CIS deduction if applicable.
- Reconcile against the bank. Payments received should match invoices marked paid. Anything paid but unmarked, or invoiced but unpaid, gets fixed now, not in January.
- Save the file with a name and a place:
invoices-2026-03.csvin a year folder. Cloud or drive, just consistent. - Keep contractor statements in the same folder. For CIS subcontractors, the monthly deduction statements are the evidence behind the CIS column.
At 5 April, year end is a merge of twelve files and a handover, not a rescue operation.
What a good CSV contains
The columns that decide whether an accountant can use the export without questions:
- Invoice number: continuous, no gaps, no restarts.
- Invoice date: the date the invoice was issued, not the work date.
- Customer name, as it appears on the invoice.
- Net, VAT, gross, separate columns; a single “total” column forces manual splits.
- VAT rate or a reverse-charge marker: for construction work, the reverse-charge invoices must be identifiable. See the reverse-charge invoice requirements.
- Labour and materials split for subcontract work, because CIS deductions apply to labour only.
- Status and payment date: paid, part-paid, unpaid, and when money actually landed.
If your software’s export misses any of these, check the settings before you assume. Most tools can include custom columns.
CIS subcontractors: what the export must prove
For a CIS subcontractor, the year-end question is always: how much was deducted, by which contractor, and does it match HMRC’s record?
- Each invoice’s labour value, deduction rate and deduction amount should be visible in the export: the rates are 20%, 30% or 0% by status.
- At year end, your total deductions claimed on the return must match what contractors reported to HMRC. If the numbers disagree, the discrepancy is found in your records, not argued from memory.
- Deductions suffered are not always refunded: they offset income tax and Class 4 NIC. If your deductions exceeded your liability, the excess is repaid, and your export is the evidence.
A CSV with a CIS column turns that reconciliation into a filter. Without it, it becomes a per-invoice reconstruction your accountant charges for.
If you are VAT registered
Two extras on the export:
- The VAT fraction or rate per line, so the accountant can check the return against the invoices.
- Reverse-charge rows marked clearly, they appear in both output and input tax boxes, and a mixed-up reverse-charge row is a common VAT return correction.
Making Tax Digital for Income Tax (from April 2026 for self-employed people and landlords with qualifying income over £50,000) pushes records fully digital and quarterly, exports stop being a convenience and become the compliance mechanism.
Handing over to the accountant
The handover that gets a fast, cheap job:
- The merged CSV of the year (or twelve monthly files).
- CIS deduction statements from every contractor.
- Expense records, summarised by category.
- Bank statements for the business account.
- The final customer statements for anything still unpaid: the accountant needs year-end debtors, which the unpaid-invoice status column gives them.
Ask your accountant what format they want before exporting; many have a preferred column layout, and most can import the standard shape.
FAQ
What CSV data does my accountant need from my invoices?
One row per invoice with number, date, customer, description, net, VAT, gross, payment status and payment date: plus CIS deduction amounts if you subcontract, and a reverse-charge marker if you do construction work.
How often should I export my invoices?
Monthly. A ten-minute export-and-reconcile each month turns year end into merging twelve files instead of reconstructing a year from bank statements.
Can my accountant import my CSV directly?
Most accountants can work with a standard invoice CSV in Excel; accounting packages import CSV with a mapping step. Ask your accountant’s preferred format before the year starts, not after.
What VAT records do I keep for an invoice CSV?
The net/VAT/gross split per invoice, the rate or zero/reverse-charge treatment applied, and the date. VAT records are normally kept for at least 6 years.
How do I prove CIS deductions at year end?
With the monthly deduction statements your contractors issue, plus your own invoice records showing the labour value and deduction on each CIS invoice. Both must reconcile to HMRC’s figure.
What happens if my invoice records are incomplete?
Your accountant reconstructs turnover from bank statements, which costs fees, invites HMRC questions, and can lose you expense claims. Clean software records are the cheap insurance.
One last thing
The export costs nothing and takes minutes; the reconstruction it replaces is billed by the hour. Set the monthly reminder (last working day, export, reconcile, save) and the 5 April handover becomes forwarding twelve files instead of paying someone to guess what happened.