共同基金（互惠基金）在过去的20多年内已成为极受欢迎的投资工具。它已成为许多人日常生活的一部分。在美国有超过8000多万人，即一半的家庭投资互惠基金。根据美国投资公司协会（Investment Company Institute）的最新统计，到2007年4月，美国互惠基金的投资总额已突破11万亿美元。在加拿大人口，互惠基金投资总额也已超过7000万加元，即人均2万加元投资于互惠基金。事实上，对于大多数人来说，投资即意味着购买互惠基金。至少，投资于互惠基金比单纯把钱存入银行的支票账户和储蓄账户要好。
互惠基金，又称共同基金，是指专门的投资机构通过发行受益凭证的方式，将社会上闲散资金集中起来交由专家管理，分散投资于各种有价证券或其他行业，
投资者按投资比例分享投资收益的一种基金。
互惠基金是股票、债券及现金的一个投资组合。一个通俗的理解，是可以把互惠基金当成是一个公司，该公司聚集了一群人，他们把投资的钱集中在一起，由基金经理投资于股票、债券及其它有价证券，每个投资者拥有该公司投资的一部分，即持有该基金一定的份额。
互惠基金的特点包括：
1) 专业化管理：投资人的资金由投资专业人士管理。投资者购买基金是因为没有时间管理自己的投资组合或没有投资方面的专业技能，互惠基金为小额投资者提供了一种相对便宜的方式，由专业全职的基金经理管理和监控投资人的投资。
2) 多元化投资：投资互惠基金而不是个别的股票或债券可将投资人的投资风险分散。基金拥有大量资金可分散投资于不同行业上百只的股票和债券，其中任何一只股票或债券亏损对整个基金投资收益的影响都很小。换句话说，投资人持有的股票、债券的品种和数量越多，其中任一股票和债券价格的变动对投资人的投资的影响就越小。
3) 规模经济：互惠基金在同一时间购买和出售大量证券，其平均交易成本低于个人交易的费用。
4) 高流动性：互惠基金允许投资人将其投资随时转换成其它基金，货币市场基金或现金。
5) 购买简便：大多数基金公司按月购买计划100元即可，一次性投资500元即可。
互惠基金的收益有三种方式:
1) 利息收入：投资于固定收益的债券或货币市场基金取得的入息。
2) 股息收益：即基金的红利分配。
3) 资本增值：若持有的基金单位价格上涨，或基金持有的股票或债券价格上涨而形成的收益。
投资人可以现金的方式取得这些收益，或将投资收益用于购买更多的基金份额，虽然基金的单位价格没有增加，但投资人所持有基金的总额增加了。
隔离基金
隔离基金（Segregated Funds），或是分离基金，又叫保证基金，由保险公司管理的一种投资基金形式。之所以称之为“分离基金”，是因为这种基金是与保险公司其它资产分开管理。
分离基金除了具有互惠基金本身分散投资、降低风险及专业人士管理的特点之外，最大的优势在于其带有保障投资者本金的功能。分离基金合同规定，在约定的期间内（一般为十年），投资人所投入的本金在到期时（Maturity Date），可获得所约定的保障（75% 或 100%）。尽管不同种类的分离基金仍然存在看不同程度的风险，但是因为可以“保本”，同时在总体上比互惠基金更加稳健，所以分离基金更适合长期投资安排，特别是在投资市场波动很大的时期。
分离基金可以用于购买 RRSP 或 RESP，其投资方式灵活多样，既能一次性投资然后随时追加投资，也可以通过系统设定实现定期定额投资（Dollar Cost Averaging）。
值得说明是，不同于人们可以自己购买互惠基金或者股票，分离基金必须由具有相关执照的人员销售。
与一般的互惠基金相比，分离基金具有如下几项优势：
Creditor protection：只要指定受益人，投资人在分离基金中的资产就不受债权人的追索。此项选择非常适合于那些自己做生意的投资者，或自雇人士。
Powerful guarantees：不论市场如何变化，如基金拥有人在合同期间内去世，投资者在分离基金中的投资本金可得到合同规定的保障。通常为100％的本金。
Freedom from probate fees：分离基金合同的受益人可直接获得该项资产，可免去遗产继承过程中的法律费用等。
Lock-in the growth of your investment：在税收方面，分离基金亦较普通的互惠基金具有优势。
保本基金与互惠基金比较
Segregated Funds Vs Mutual Funds
"保本基金（Segregated Funds）"在加拿大是于1961年开始由人寿保险公司提供。这种保险公司版的互惠基金，与投资公司的互惠基金，有一些相似性，但也有许多重要差别。
下表列出了保本基金与互惠基金的一些基本差别。但除了这些基本差异之外，还有一些更重要的不同，我们在以下的文字中作了进一步说明。为了有利于读者更准确理解，说明是用英文，只对一些关键词作了中文翻译，以供参考。
| Benefit | Seg Funds | Mutual Funds |
|---|---|---|
| 到期保本 Maturity Guarantee |
Yes | No |
| 死亡保本 Death Guarantee |
Yes | No |
| 信用保护 Creditor Proofing |
Yes | No |
| 遗产保护 Probate Protection |
Yes | No |
| 保险保护 Insurance Protection |
Yes | No |
Mutual funds are regulated under the provincial securities regulators and segregated funds are regulated by the provincial insurance officials. Mutual funds are offered through a prospectus filed with the provincial securities commission and segregated funds are offered through an information folder. Most mutual funds and segregated funds are available on a deferred sales charge basis.
Like mutual funds, the segregated fund policy holder has no ownership rights in the assets of the fund. They remain the property of the insurance company. Segregated fund units and mutual fund shares are units of value, where the policy holder owns an interest but not a piece of property. According to the market value of a specified group of assets, the insurance company must maintain separate funds with separate assets for each fund.
Segregated Funds are actually variable deferred annuity contracts with insurance protection in the event of death. It is this insurance component that brings together many of the benefits of segregated funds. At death, proceeds of a segregated fund can pass directly to a named beneficiary, and are not subject to creditor's claims, probate, lawyer's or executor's fees. As long as a preferred beneficiary is designated, creditor protection exists during the policy holder's lifetime even if a bankruptcy occurs. Mutual funds don't have this protection, since, upon death, they become part of the deceased's estate and are subject to taxes, legal, executor and probate fees.
Segregated Funds offer guarantees at maturity (ten years from date of purchase) or death on the limit of potential losses - 100% of original deposits, less any withdrawals, are guaranteed which makes them an attractive alternative for the cautious and/or long term investor. No such guarantees exist for mutual funds and it is possible to have little or nothing left at death or plan maturity.
To the extent that the maturity and death guarantees of segregated funds are applicable, these same amounts are covered up to $60,000 by CompCorp, the insurance company protection association, when you have such an investment with one of CompCorps member companies. Mutual Funds are not covered in like manner under CDIC, the equivalent bank insurance coverage.
If you purchase non-registered mutual funds towards the end of a calendar year, you could pay tax for a year's worth of capital gains even though you did not own units for a whole year. With segregated funds, income is allocated monthly so you don't have to pay tax on gains that arose before you owned units.
Non-registered segregated funds have an additional tax advantage over mutual funds. If a segregated fund loses capital in a given year, the unit holders can claim the capital loss on their taxes and offset any capital gains made on other investments. Taxation rules allow the allocation of capital gains or losses without cashing in the units held. Mutual funds do not have the ability to allocate. They distribute gains or losses and a loss cannot be distributed. The only way to declare a loss with a mutual fund is to sell the units held.