When to switch accounting software: year start or mid-year

What is a cut-over date?

A cut-over date is the day your new accounting software becomes the only place where new transactions are recorded. Everything before that date stays in the old system as the archive. Everything from that date onwards goes into the new one, starting from opening balances.

The line has to be sharp. A bill dated the day before belongs in the old system, even if it arrives a week later. Most switching problems come from a blurred line, not from the date.

Is the start of the financial year the best day to switch?

The first day of your financial year, 1 January, 1 April or 1 July depending on where you trade, is the cleanest day to switch because the year, the invoice series and the tax registers all start fresh on the same day. Your old system holds one complete year and your new system starts the next one.

• One year, one system. The profit and loss for the closed year comes from the old software alone, and the new year from the new software alone.
• One set of tax registers per system per year. The sales and purchase registers your accountant checks for VAT, GST or sales tax returns come from one place for each period.
• Numbering restarts cleanly. A series that carries the year, such as INV-2026-0001, begins at 0001 at the year start anyway, so there is no gap or overlap to explain.
• Opening balances are year-end balances. The closing trial balance at the year end is usually reviewed by your accountant already.

The cost of waiting is real, though. Half way through the year, waiting for the next year start means six more months of an old setup that is already failing you.

Can you switch accounting software in the middle of the year?

Yes, a mid-year switch is safe if you cut over on the first day of a month, take a trial balance on the last day of the previous month, and keep both systems' sales and purchase registers for the split period. The extra work is mostly for your accountant at year end.

The first day of a month matters because tax returns are prepared for whole months or quarters. If you switch on 1 October, September sits entirely in the old system and October entirely in the new one. Switch on 17 October and the October figures need two registers added together.

Which cut-over date suits your business?

The right date depends on how much the old system is costing you now and how much year-end work a split year adds. Use this table with your accountant.

What does a mid-year cut-over look like with real numbers?

Harbour Steel Furniture, the fictional business on this site, decided in September 2026 not to wait for the year start. It chose 1 October 2026 as the cut-over date and took this trial balance from its old software at the close of 30 September, with amounts in US dollars.

Every line becomes an opening balance on 1 October. Customer and supplier totals go in party by party, so each statement of account opens with the right balance. Stock goes in by product with quantity and cost. Reserves and profit of $23,560 sit in equity as one opening figure; the detailed profit and loss for the year to September stays in the old software, which is the archive for those months.

1. 1

   30 September, evening: close the old system

   Post the last invoices and bills, count stock, and take the trial balance, receivables and payables by party, and the September sales and purchase registers.

2. 2

   1 October: enter opening balances

   Enter every trial balance line, with parties and products in detail, and check the new trial balance matches.

3. 3

   1 October: freeze the old period

   Once the figures match, set a lock date of 30 September in the new system.

4. 4

   1 to 14 October: dry run

   Raise each real invoice in both systems and compare the totals each week.

5. 5

   15 October: go live

   Stop all entries in the old system and keep it read-only as the archive.

What does your accountant need for each choice?

Your accountant needs a trial balance at the cut-over date and the sales and purchase registers from whichever system held each month.

• The cut-over date is the 1st of a month and written down
• The old system's trial balance at the day before cut-over balances
• Receivables and payables add up to the control accounts in that trial balance
• Stock counted, and its value matches the inventory line
• Sales and purchase registers for every month before cut-over exported from the old system
• The new system's trial balance after opening balances matches the old one line for line
• A lock date set at the day before cut-over
• The old system kept, read-only, as the archive

Why does a lock date matter after you switch?

A lock date freezes every period up to that date, so nobody can post a backdated entry into a month you have already handed to your accountant. After a cut-over, it protects the opening balances: once they are agreed, they cannot move.

Without one, a late bill dated 28 September can be entered in the new system and quietly change a September figure that came from the old software. Set the lock date to the day before cut-over as soon as the opening balances match.

Why does invoice numbering restart cleanly at the year start?

Most tax authorities expect invoice numbers to be unique and in sequence, so a series that carries the year in it can restart at 0001 every year without clashing with last year. A number such as INV-2026-0001 is short, clear and sorts in order.

On a year-start switch, the new system simply starts the new year's series. On a mid-year switch, agree the next number with your accountant so the series continues without a gap or a duplicate, or start a separate series for the rest of the year.

How does SimpleERP handle either cut-over date?

SimpleERP has an opening balances wizard that takes the trial balance per account, and receivables and payables per party, with any difference going to Opening Balance Equity. Opening stock goes in by product, by stock adjustment or by import. Customers, suppliers, balances and open bills can be imported from a spreadsheet or a Zoho Books export, dated by the cut-over. One accounting lock date then freezes the old period.

• Invoice numbering by financial year, such as INV-2026-0001, which restarts at your year start.
• Sales and purchase registers for the months in SimpleERP, to sit beside the old system's registers.
• Trial balance, profit and loss and balance sheet, each with CSV export for your accountant.

Read how to switch from spreadsheets to cloud ERP for the whole move, or see how SimpleERP compares with QuickBooks.