vAT collectability

Hi,

If I only invoice my services provided in March at the beginning of April, does this invoice belong in quarter 1 (because the services provided were still in quarter 1) or does it belong in quarter 2 (because the invoice date is April)?

I found this in the learning center:

This includes all your purchases and sales with an invoice date between 1 January and 31 March. These are automatically bundled in Dexxter and stopped in the vAT declaration for quarter 1.”

However, I read some confusing information online, which is why I am asking for clarification.

Thanks in advance for your answer! 🙂