请问：limited tax GO debt  和 unlimited tax GO debt怎么理解啊？

这个应该是市政债券，以市政府的税收能力作为保证，根据级别的不同，分为有限责任和无限责任的，这可能与美国政府具有破产的权利有关。

google一点,供探讨：

Limited Tax GO Bounds

A limited tax GO bond is a general obligation bond secured by the plege of a specified tax, or category of taxes, and includes a limited rate or amount. Policies on this form of debt record the amount of limited tax GO debt that can be issued and the circumstances under which it can be issued. The amount of allowable limited tax GO debt may already be capped by state statute in some states(e.g., to 10 percent of assessed property value without voter approval). In these cases, a local government should indicate the state cap in its policies.

所以愚以为limited 是指tax的rate或者amount是否是limited 的。

反之unlimited似乎是指是否可以无限发行tax 来支持这些bonds的retirement.下面是一段查到的Oregon/Portland的市政对于Outstanding Long Term Debt的披露：

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Unlimited Tax General Obligation Bonds

Tax supported General Obligation Bonds

The City has $61.77 million of outstanding tax-supported general obligation bonds. These bonds were originally issued for the purpose of funding park and emergency facility system improvements. The City is authorized to levy an unlimited ad valorem tax to pay these bonds.

Self-Supporting General Obligation Water Bonds

The city has $4.63 million of outstanding self-supporting general obligatio water bonds. While the city has the authority to levy an unlimited ad valorem tax to pay these bonds, the City has chosen to pay these bonds entirely from revenues of the water system.