Can Project Start date and end date be independent to Task dates for processing transactions

Dear All

Our business needs are where we create a project with start and end date and make transactions,. but Only after receiving final progress report we process the payments. So sometimes we received these final progress reports many months after the project start date and end date . and the transactions are refused by Finance as GL periods are open and they cannot open previous years GL periods etc.

So is there a way that in the Task dates should be independent to Trans Duration.

Kindly Suggest.

Thanks