Is there any way to link these sales order to the old contracts.
Suggestion:
If your sales order has subsequent documents then it is not possible to link to your old contracts. For such orders this option will be disabled.
For those order that don't have subsequent orders:
Goto VA02 T.Code.
Enter the order number.
Enter.
Ensure that the customer numbers are same in both. If not change the customer number in order. After that Click on Sales document-->Create with reference. While changing the customer the taxes will be redetermined.
Enter your contract number.
Click on copy.
New material will be added here to your old one. If you want then you can keep this or delete the material of your order and then save.
Or you can assign your sales order to contract also.
Goto VA02,Enter your order number. Edit-->Assign contract. Here you can assign either Header or item also.
or
If Customer, materials are same in the Contract and Sales Order, this is possible.
Go to VA02, from the menu bar Edit--> Assign contract.
or
As far I know when you have created the document i.e. a Sales Order without any reference be it "CONTRACT", then on later stage you cannot link it. I would suggest you to follow the following steps:
1. Go to T-code "VA02", Select that Sales Order and enter to change mode. Here you delete the item of the Sales Order.
2. Then Create a Fresh Sales Order with reference to a Contract.
