I just found out about this program. Can I claim SR&ED credits for work done in previous years?
Yes. Although you should file the appropriate forms with your tax return, if that is not possible, you must file the form no later than 12 months after the filing due date of your tax return. For corporations, this results in a deadline of 18 months from the end of the taxation year in which the expenditures were incurred, while individuals have 17 ½ months.
Reference: An Introduction to the SR&ED Program.