Can I import my old invoices into new software?

Sometimes, and it matters less than people expect. Most tools import a client list happily and historical invoices badly, because every vendor's export is a different shape. The records you must keep for HMRC are satisfied by the exported files themselves, so a clean client import plus an archived folder of old invoices is usually the faster and safer outcome than a messy historical import.

How long do I have to keep records after switching?

Six years from the relevant filing deadline is the figure to work to for a sole trader. Keep the exports for that long regardless of what the new software holds, and keep them somewhere that is not one laptop.

Should my invoice numbers restart in the new system?

No. Continue the sequence you were on. Unique and consistent is what matters, gaps are acceptable, and duplicates are the thing to avoid, because two documents sharing one number is genuinely ambiguous at tax time and on the phone.

How to switch invoicing software without losing your records

By Sage Vinson · Updated 16 August 2026

Switching goes wrong in one of four ways, and all of them are avoidable in an afternoon. You cancel before you export and the history goes with the account. You keep less than HMRC can ask for. You move halfway through a job and a quote falls down the gap. Or you restart your invoice numbering at 1 and hand an inspector something to pick at. Here is the order to do it in.

Export first, cancel second

The moment a subscription lapses, most software puts your data behind a paywall or deletes it on a timer. Whatever the marketing said about owning your records, the practical version is that you can read them while you are paying and often not afterwards. So the export happens while the old account is still live and still paid.

Take clients, invoice history, quotes, and anything with a number on it. CSV is fine and usually the only option. Download the PDFs of issued invoices as well as the spreadsheet, because a row in a CSV is not the document you sent and it is the document that settles an argument about what was agreed.

Client list, with addresses and phone numbers.
Every invoice raised, paid and unpaid, as data and as PDFs.
Quotes, especially any still open.
Anything you have attached to a job: photos, certificates, signed acceptances.

Keep six years of records

HMRC can ask a sole trader to produce business records going back six years from the filing deadline, and "it was in the old app" is not an answer they have to accept. That is the number that decides how much history you carry across, not how much the new software makes it convenient to import.

You do not have to load six years into the new system. You do have to be able to produce it. A dated folder of exported CSVs and PDFs on a drive you actually back up satisfies that perfectly well, and it is faster than fighting an importer that was never designed for another vendor's export.

Carry your invoice numbering across

Start the new system at the next number in your existing sequence. If you finished on 214, the first invoice out of the new tool is 215. Every invoicing tool wants to start you at 1 or 1001, and accepting that default is how one business ends up with two invoice 001s in the same tax year.

Gaps in a sequence are explainable. Duplicates are not, because a duplicate number means two different documents claim to be the same invoice, and which one the customer paid becomes a matter of opinion. Most tools let you set the next number in settings before you send anything. Do it before the first invoice, not after.

Don't move mid-job

Finish and invoice what is open, then switch on the quiet week. A job that is quoted in one system and invoiced in another is a job where the quote and the invoice can disagree with nobody noticing, and it is the single most common way a switch costs real money.

If a big job is going to run for months and there is no quiet week coming, run both systems for that one job only and close it out in the old tool. Paying for one extra month of the old subscription is cheaper than a lost variation.

Before you cancel the old account

Two things outlive the software and are easy to forget, because they are not inside it. Any payment link on an unpaid invoice you already sent may be tied to the old account, so a customer paying late could hit a dead link. And any recurring invoices or automatic reminders that were running will stop, quietly, without telling the customer or you.

Check for both, send fresh invoices for anything still outstanding, and only then cancel.

Common questions

Can I import my old invoices into new software?: Sometimes, and it matters less than people expect. Most tools import a client list happily and historical invoices badly, because every vendor's export is a different shape. The records you must keep for HMRC are satisfied by the exported files themselves, so a clean client import plus an archived folder of old invoices is usually the faster and safer outcome than a messy historical import.
How long do I have to keep records after switching?: Six years from the relevant filing deadline is the figure to work to for a sole trader. Keep the exports for that long regardless of what the new software holds, and keep them somewhere that is not one laptop.
Should my invoice numbers restart in the new system?: No. Continue the sequence you were on. Unique and consistent is what matters, gaps are acceptable, and duplicates are the thing to avoid, because two documents sharing one number is genuinely ambiguous at tax time and on the phone.

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