Maternity offset results in negative net on full month

Summary

Resulting in negative net pay

Content

We are due to launch Cloud Payroll tomorrow! 

We are using statutory payments calculations to derive salary offsets where an employee is on maternity. 

However the formula rounding pushes the employees into negative net (by a few pence), this is a showstopper! Why would the seeded formula process an offset that is greater than one months salary(?). 

Please can we have some urgent action whereby we need a formula that we can apply where an employee is on maternity for a full month, so that the offset is never greater than a calendar month of salary?