Please explain to me the concept of resource related billing and its different between periodic and milestone.  In what kind of business scenario do we use it? and what are the settings required to use it?

Periodic billing is used when you want to bill the customer at different points of time based on the periodicity or progress of the work. 

Milestone billing can be used for this type of billing purposes when you want to have billing control from the project.

Resource billing is based on the resource consumption for the particular activities. Dynamic Item Processor (DIP) profile is used for the resource related billing.

Steps to be followed:

1) Configure DIP Profile (T.code ODP1)

2) Specify the usage - 
(i) Billing & Result Analysis (RRB)
(ii) Request Quotation (Sales Pricing)

3) Specify - 
(i) Sales Document Type (PS2)
(ii) SD Doc Type CMR 

4) In Sales Order Type --> Sales Order Category - "L" (Debit Memo Request)

5) Document Pricing Procedure --> PS (Customer Project)

6) Select the billing usage and click on characteristics. eg--> Activity Type

7) Then define sources. Select "Actual Cost" as we use actual cost for RRB. Define%

8) Sources --> Selection Criteria: This would display all characteristics. Now in Activity Type --> Mention the activity type

9) If more activity type are being used then create set of activity type using T.code GS01

10) Material Determination --> Initially create material with "Material Type = Service"

11) The service material should be mentioned in the material determination

12) Criteria -- In criteria allocate the activity type for the specific material. (We can also use cost element, cost center, which we have defined in characteristics)

13) Create Project (T.code CJ20N)

14) Create Sales Order (T.code VA01)

15) Book CATS 

16) Execute DP91 to view Sales Pricing
 

Common Errors:
AD01-155: Error during material determination for sales document item. Material Origin field was not checked in the Costing tab of the material master.
IX-057: No cost management is provided for sales document (contract) item. This is usually because there is no requirements type assigned to the contract item (see procurement tab).
No material appears in DMR/CMR. In the material master costing view, set the "Material Origin" checkbox (see OSS note 174382)
No expenditure item found.

Go back to the service order and check there are actual costs 

Check your DIP Profile; specifically the sources section to ensure you are not filtering out any dynamic items.

CO Configuration:

KL03: Check activity type validity dates

KA03: Check cost element validity dates

KA03: For labour, check cost element category is 43

KA03: Check if Record qty flag is set on Indicators tab

KA03: Check cost element assigned to your controlling area

KP26: Check that activity type is linked to cost centre

KP26: Check that there is a rate for the activity type/cost centre 

KP26: Check are you using the correct version

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