Assign customer numbers automatically

Since Modified does not automatically assign its own customer numbers, there are two variants here.

Variant 1: Simply increment the customer number.

We start with a number that you give us, e.g. 1000, and then we simply count up from there.

Variant 2: Customer number from date and suffix

The customer gets a number consisting of day, month, year and an ascending number,
for example 30122016-75, then it would be the 75th customer who registered on 30.12.2016.

Variant 3: Structure of your choice (please explain in detail in the comments field in the checkout process)