From Ascgroup

Is it necessary to have a variation in quantity clause to use the TF!© software?

No. While some contracts using the TF!© software do have a variation in quantity clause, it is not necessary to have a variation in quantity clause to use the TF!© software. The TF!© software can support any type of basis of payment. Since service contracts that involve base operations and maintenance or other services and are subject to some level of normal variation, best practice suggest there be some predefined methodology established to handle the inevitable changes to scopes over time. The methodology established should seek to mitigate the contractor’s sole source negotiating advantage, and whichever methodology is chosen for a specific contract, it can be readily accommodated in the TF!© software.