Money donated to most Chapters and SIGs is NOT tax deductible as a charitable contributions, according to U.S.A. tax law. (Laws may vary in other countries.)
For example, ACBS is a non-profit, tax designation 501(c)6.
Charitible non-profits (or those grandfathered in), are 501(c)3, and contributions to them would be tax deductible (as a charitable contribution... as a donation to the Red Cross would be).
Membership dues paid to ACBS or a Chapter, according to US tax law, are not tax deductible, but may be deductible to the individual as a business expense.
501(c)6 groups may accept donations (without the expectation that they will be tax deductible), but the US IRS has very specific requirements that these donations may only be solicited if you make it very clear that they are not tax deductible. (This statement must be on its own line/paragraph, must be in font as large as the request for donations, etc.)
Again, tax law outside of the USA may vary.