We have not been writing fixed-price offers for a long time. For these, long specifications are written in which all requirements are compiled. These specifications must be adhered to, as the price is fixed.
This does not apply to Agil: The offer includes a daily rate as well as an offer appendix in the form of a backlog with the roughly defined tasks and time estimates. Billing is usually monthly and includes exactly the time we needed for the implementation - no more and no less.
The backlog differentiates between must/should/can requirements. This enables a go live with the MVP, the Minimum Viable Product (with all must-have requirements), and further development can be done individually. During development, the backlog is constantly refined and adapted, so it is just as agile as the whole way of working. At the same time, the backlog is in no way fixed. Items can be added or removed at any time, in consultation with our customers.
This saves us long test phases and waiting times for the completion of the product. The employees and customers can have their say and tell us where the shoe pinches the most. This is exactly the point where we continue to work.