Your group should decide this, keeping in mind their prudent reserve requirement. Many groups have chosen to send donations quarterly. Often, donations are split using a 60/30/10 formula, with 60% of contributions to intergroup/service board, 30% to WSO, and 10% to region. As with frequency of contributions, this is a matter for your group conscience. 

There are a few meetings in our intergroup/service board which make no contributions to WSO, region, or service board/intergroup. How do I approach this issue to see what’s going on? 

Your intergroup/service board treasurer can get actively involved with all the group treasurers so that oversight of group contributions is easier. Voicemail or email contact can facilitate this process. The intergroup treasurer can visit non-contributing meetings and share about self-support and read from the Seventh Tradition pamphlet. Groups that do contribute should be sent acknowledgements or thank you notes for their contributions. Read Fundraising and Prudent Reserve Guidelines for Groups and Service Bodies for more information.