This question comes from a young pastor friend who has recently taken his first pastorate:
Question: Do you allow congregants to designate their giving, or do you require all tithes & offerings to go into the general fund?
Most congregations only allow designated giving in certain situations. Normally, all funds received are used to offset the general fund regardless if the gift is designated or not. For example, let's suppose a church has already decided to spend $2,000 on Vacation Bible School. Generally speaking, if someone puts a check in the offering plate for $500 designated to VBS this does not mean the church can now spend $2,500. The $500 is simply used to offset what the congregation has already previously decided to spend. The rationale for this is that the congregation and leaders have prayerfully enacted a financial plan and that all monies spent must be in accordance with this plan. Once people begin to "designate" gifts then the idea of a unified and cooperative budget goes out the window. One person should not be able to override what an entire congregation has decided, regardless of how noble the motive.
Most typically we experience this situation with missionaries. Individuals who honestly want to show love and support for missionaries sometimes designate additional funds to a specific individual or missionary family. However, our support level for that specific ministry worker has already been set by the congregation and therefore designated gifts will only offset (and never add) to what a missionary receives. If individual congregants truly want the missionary to receive additional funds we instruct them to send the money directly to him.
However, most churches allow designated giving for certain situations. Our church allows designations to be made for a handful of programs, such as benevolent fund, Christmas missionary fund, and our Bible Camp program. We also sometimes open temporary ways to designate giving, such as a Summer youth missions project (however, the IRS requires non-profits to inform donors that the organization is not required to honor any designations).
Of course, various churches would disagree about some minor details, but this seems to be the general practice of most congregations.