Revenue Canada regulations for donations to qualify as a tax deduction on their 2008 income tax return: 

• If mailed in: Envelope must be postmarked on or before December 31, 2008
• If turned in: Donation must be deposited on or before December 31, 2008. Any donations handed in, on or after 1/1/09, regardless of the check date must be treated as 2009 donations.

Canada Revenue also advises: 

 To ensure your church contributions are tax deductible, do not file your 2008 income tax return until you have received a written acknowledgement of your contributions from the church. Donation receipts will be mail by the end of January.