An ad hoc request is a scoped piece of work that must be:
An ad hoc request may be used when the work to be delivered can be accurately estimated at the time of placing the request. Any change to the original request requires a new estimate and a new pricing.
Ad hoc requests are estimated according to an agreed complexity matrix that takes into account the type of development and the complexity of the development. Criteria should be in place to categorize the complexity.
This type of contract would likely be used for work that do not exceed 15 days and can be split into clearly identified pieces:
A time & materials contract provides for acquiring services and/or products on the basis of:
A time-and-materials contract may be used only when it is not possible at the time of placing the contract to estimate accurately the extent or duration of the work or to anticipate costs with any reasonable degree of confidence.
Such contracts use a fixed hourly rate, and are based on 8 hours per day work during the total length of the contracts. The number of days per week and/or month is determined upfront but can vary between contracts.
This type of contract would likely be used for work estimated upfront to cover the duration of the contract:
A package contract is a convenient way for acquiring support services with following limitations:
A package contract is a variation of a time-and-materials contract. However no end date is promised and hours are not necessary spent continuously and by means of full days.
Such contracts use a fixed hourly rate by chunks of hours, i.e. the more hours are purchased, and the cheaper the hourly price is.
This type of contract would likely be used for support activities: