The Finance Department has published new rules that come into effect in the new year, but says it won't implement a mandatory 21-day interest-free grace period until next September.

The announcement posted on the department website says that starting January 1, credit card issuers must provide a ''summary box'' on application forms detailing interest rates and fees.

As well, banks must inform clients how long it will take to repay their balance if they only make minimum payments each month, give notice of changes in interest rates and require approval before increasing the credit limit on a card.

Canada's banks opposed the reforms during public hearings earlier this year, saying the changes were unneeded and costly and noted that 70 per cent of users paid their bills in full on time.

Critics, however, called on the government to go much further, including limiting the top interest rate that could be charged on cards.

The government statement gave no reason why it was delaying enacting the 21-day grace period until September. The grace period would prevent banks from charging interest on all new credit card purchases when a customer pays the outstanding balance in full.