Best answer by Nancy_OVO
There are two different volumes that gas usage can be measured in. Either hundreds of cubic feet (HCF), or cubic meters (M3).
Generally speaking, older gas meters measure in HCF and newer meters (and smart meters) measure in M3. HCF (or, Imperial) readings only have four digits, as its a larger volume overall so the numbers used at domestic supply would stay fairly low. M3 (or metric) readings have five digits as its a smaller volume and households can get through more.
If your online account is still asking for a four digit reading, the likelyhood is that we haven't received the new meter details from the engineers to add to your account. It can take 6 to 8 weeks to do this, after which you online account should be asking for five digits.
You won't be billed while we're waiting for the meter details to come through. Once we've got them, we'll bill your old meter up to he last reading the engineer took, and then add the new meter (probably starting from 0).
Let me know if you have any more questions!