Interim managers will typically calculate their daily rates according to a number of factors, including:

Duration of assignment: Interims will often be more flexible on rates for longer assignments which offer a high degree of financial security.
Location: Interims usually charge a premium for travelling long distances and staying away from home.
Length of track record as an interim manager: More experienced Interims can be more effective at negotiating higher rates as employers have greater confidence in their ability to deliver.
Market conditions and level of competition from other interim managers: During times of low demand for Interims or where there is a high degree of competition between interims for assignments there is a tendency for greater flexibility on rates in order to secure positions.
Level of satisfaction gained from assignment: Interims are usually prepared to accept lower rates for assignments which are deemed to be interesting and provide job satisfaction.
Amount of CV enhancing experience gained: If assignments add significant value to an interim's CV and increase the chances of obtaining further work then greater flexibility of rates is often demonstrated.

Guidance rates payable to interim managers by McGinley Interim Executives:

Chief Executive: £1200+
Director: £1000+
Programme Manager: £1000+
Leadership/General Management: £750+
Operations Management: £650+
Finance: £500+
IT: £500+
HR: £500+
Project Management: £500+