Moving your company’s filing to new software: what to bring from last year
Your first year in new filing software only works if it starts where last year ended. That means last year’s balance sheet as opening balances, and the tax figures that carry forward from one return to the next: losses, capital allowance pools and any director’s loan. Get these together before you start, not at the deadline.
- Start from last year’s closing balance sheet. It becomes this year’s opening balances.
- Bring the tax figures that carry forward: unused losses, capital allowance pools and any director’s loan.
- List last year’s unpaid invoices and bills, so this year’s payments have something to match.
- Your accounts filed at Companies House are free to download from the register if you don’t have a copy.
- Have your UTR, Companies House authentication code and Government Gateway details ready.
A4O Accounts prepares the CT600 from your books and files it with HMRC. See the CT600 software, or get started free.
Why last year matters
HMRC’s free filing service closed on 31 March 2026, so many companies are filing through new software for the first time. See what to do now the service has closed.
New software knows nothing about your company’s history. This year’s figures depend on last year’s in three ways:
- The balance sheet carries on. The bank balance, money owed to and by the company, and the director’s loan on the last day of last year are where this year starts.
- The accounts show last year alongside this year. Last year’s figures appear next to this year’s in the accounts you file.
- Some tax figures only live in last year’s computation. Losses and capital allowance pools aren’t in the accounts. If you don’t bring them, the new computation starts from nothing and you may pay more tax than you need to. See what goes in a Corporation Tax computation.
What to bring
| What | Where you’ll find it | What it’s used for |
|---|---|---|
| Last year’s balance sheet | Last year’s accounts | Opening balances, and last year’s figures in this year’s accounts |
| Last year’s profit and loss account | Last year’s accounts | Last year’s figures in this year’s accounts |
| Losses carried forward | Last year’s computation and CT600 | Taken off this year’s taxable profit |
| Capital allowance pools | Last year’s computation | This year’s writing down allowances |
| Director’s loan balance | Last year’s balance sheet, and CT600A if you filed one | Whether s455 tax is due or can be reclaimed |
| Unpaid invoices and bills at the year end | Your old bookkeeping, or your own records | Matching this year’s payments to them |
| Corporation Tax owed for last year | Last year’s computation | Clearing it when you pay HMRC this year |
The balance sheet: your opening balances
Take each figure on last year’s closing balance sheet and enter it as an opening balance on the first day of this year: fixed assets, stock, money owed to you, cash at bank, money you owe, and the share capital and reserves. The balances must add up to zero, the same way the balance sheet balances.
Two things catch people out:
- Use the filed accounts, not a draft. The opening balances have to match what was filed, or this year’s accounts won’t agree with last year’s.
- Break the totals down where you can. A single figure for “debtors” works for the accounts, but a list of who owes what lets you match each payment when it arrives.
Losses carried forward
GOV.UK says a trading loss you haven’t used can be carried forward and set against future profits. The figure is in last year’s computation, and on the CT600. If the company made a loss last year, or has a loss left from an earlier year, bring the amount still unused.
Capital allowance pools
When the company buys equipment that isn’t claimed in full straight away, the remaining cost goes into a pool. GOV.UK explains that each year you claim a writing down allowance on what’s in the pool: 18% for the main pool and 6% for the special rate pool. What’s left carries forward to the next year.
Bring the closing value of each pool from last year’s computation. If you claimed the Annual Investment Allowance on everything you bought, the pools may be empty, which is worth knowing too.
Director’s loan account
If a director owed the company money at the year end, check whether it was repaid. GOV.UK says the company pays extra tax, called s455, on a loan still unpaid 9 months and 1 day after the year end, and can reclaim it once the loan is repaid. Bring the closing balance and any s455 paid. See CT600A: loans to participators.
If you filed through HMRC’s old service
You typed your figures into HMRC’s online forms, so the accounts and computation came from there.
- Accounts: accounts filed at Companies House are public. Search for your company on the Companies House register and download them free from the filing history.
- The computation and CT600: look for the copy you saved when you filed. The losses and capital allowance figures you need are in it.
- If you can’t find a copy: ask whoever prepared last year’s figures, or rebuild the pools from the purchases and allowances in each year’s accounts. Don’t guess, because the new computation depends on them.
If you’re moving from other software
Before you leave the old software, export:
- the trial balance at last year’s end
- the list of unpaid invoices (aged debtors) and unpaid bills (aged creditors)
- the fixed asset register
- last year’s accounts and computation as PDFs
Keep a copy of everything. HMRC can ask to see your records, and you can’t count on still having access to the old software later.
What else you need to file
- Your company’s 10-digit UTR for the Company Tax Return
- Your Companies House authentication code for the accounts. See where to find it
- Your Government Gateway user ID and password when you file the return
Your deadlines don’t change when you change software. See Corporation Tax deadlines.
Moving to A4O Accounts
In A4O Accounts, you set the opening balance date and enter last year’s closing balances as a journal. Then you import this year’s bank statements as CSV, Excel or OFX files. At the year end, the accounts and the tax computation are built from those books, and the CT600 is filled in from the computation. Have your losses and capital allowance pools to hand for the computation. See moving across from HMRC’s service, what you can file and CT600 software: what to look for.
More in this series: all the CT600 guides.
File your accounts and Company Tax Return from one set of books
A4O Accounts prepares your accounts and CT600 from the same figures, tags them in iXBRL and files them with Companies House and HMRC. Free to get started, no card required.
Get started freeSources
- GOV.UK — Filing company accounts and tax returns if you previously used the HMRC online service
- GOV.UK — Company Tax Returns
- GOV.UK — Corporation Tax: calculating and claiming a loss
- GOV.UK — Capital allowances: writing down allowances
- GOV.UK — Directors’ loans
- Companies House — Find and update company information
This guide is general information, not tax or legal advice. Rules change, so check GOV.UK or ask an accountant about your company’s situation.