Hi crydesignltd,
Thanks for your Question, welcome back to the Community Page
With all things like this, it's worth speaking to HMRC or a Tax Specialist Accountant, about the effects on your VAT. I'm not really in a position to tell you what to do here, as I'm not qualified to do so.
However, I am able to tell you that if you are changing the date on an invoice, and the date of this happens to move from one period to the next for example on your VAT return, it will create an exception to facilitate this. You can read more about exceptions and the subsequent VAT Exception Report here: https://quickbooks.intuit.com/community/VAT/VAT-exceptions-and-reports/m-p/239631
If you speak to HMRC, they may advise you to Unfile your return with us, make your amendment and resubmit it; if they do advise you to do this, you just need to contact our Support Team who will verify some information with you and Unfile the VAT Return.
Is this an amendment that can be referenced somewhere else on the invoice, perhaps in the Memo or Description boxes? On invoices, you can select a "Service Date" column, which won't change the date of the invoice for VAT references, but can reference a date that work was carried out on? Open the invoice, click the little cog in the top right hand corner of the invoice creation page and select "Date" in the tick box.
