Correct meter reading

Hiya,
I am new to bulb, just set up today, I took over the lease of the house from the 21/12 but can only give you an online reading for today, how do I submit the reading I took the on the 21st so that everything is up to date?

Just to clarify, bulb were already the supplier

I’d phone them up so that the reading can be logged with the correct opening date. There’s no way to submit online a reading for a different date, unfortunately.