Our billing system works as such:
5th of the month = our billing date for all monthly payments
5th = everyone's shares are attempted
8th = everyone's shares are re-attempted if anything is unpaid
11th = everyone's shares are re-attempted if anything is unpaid again
16th = the remaining amount is collected from those who can pay
At any point before or after the morning of the 15th, any user can make a payment proactively towards the cost too. So you can actively choose to cover one-another, or if a payment has failed due to whatever reason, then that person can proactively pay too rather than wait for another billing day.
We track this:
Each time someone covers for someone else, it's tracked in acasa. The dashboard will show that the person who didn't paid is still "down" by £X but those who covered them will go up. This means that:
1. Your bills are paid on time
2. Whoever was covered is clear who they owe and how much
With acasa you don't always have to be 'all square' as we call it. Instead that person who is down, can simply go and buy the next set of things. Effectively start paying back everyone in toilet roll, pizza, washing up liquid or whatever :) Of course, they can also send actual money to anyone in the house too.