Send the following: 1 • the application forms, (You are in an occupation which corresponds to the list of occupations identified in the Ministerial Instructions) • a photocopy of your passport’s bio-data page, (principal applicant only) • 2 self-addressed mailing labels one in English or French and the second in the official language of your country, and • the payment.
"Do not send other supporting documents. Wait until you receive correspondence from the CIU in Sydney, Nova Scotia Canada"
So, i think u can sit for IELTS after lodging the application.
As the processing time is reducing now(6 to 12 month according to CIC) I think it will be better if I sit for IELTS just before applying to make sure that I am geeting targeted score in english and also reaching qualifying score 67.CIC may require docs whithin 6 to 8 month after application.Than I will submmit my IELTS score as it will aslo be valid till than.
For immigration purposes, if you take it within one year of your application date, it is valid for that application. Even if your application takes 10 years (hopefully not) it would still be valid if it's taken within 1 year of application. That's why if you want to calculate your points correctly, it's better to take it before you apply because you know it will be valid when CIC asks for it, even if that is 2 or 3 years from now. Look at page 9 and 10 in the application guide at http://www.cic.gc.ca/english/pdf/kits/guides/EG7.pdf