Ambarnagar Municipal Corporation's water revenue bond has net revenue of Rs 180 crore against debt service of Rs 120 crore and a 1.25x rate covenant. Tariffs are frozen for three years while costs rise 6% a year. What happens to coverage, and what does it mean for the credit?

Coverage falls from 1.50x to 1.40x, 1.29x and then 1.18x, breaching the 1.25x rate covenant in year 3. Debt is still paid, and a tariff rise of only 2.2% would cure the breach. The worry is not the arithmetic but the decision: for a revenue bond the tariff setting is the credit, and a council willing to freeze for three years could freeze for five, when cash stops covering debt service.

A general obligation of a city is backed by its whole tax base. A revenue bondA bond repaid only from the income of one project or utility, such as water charges or tolls, with no claim on any other revenue of the issuer. is backed by one stream of income and nothing else. Think of lending to a family against one child's salary only: the loan is as good as that salary and the family's willingness to keep it flowing to you. Here bondholders can look only to water charges minus the cost of supplying water, so anything that squeezes that gap squeezes them directly.

Revenue is stuck at Rs 380 crore while costs compound at 6%. Because costs are more than half of revenue, a 6% rise in costs cuts net revenue by about 7% in the first year and faster after that. Net revenue goes Rs 168.0, 155.3 and 141.8 crore, so cover goes 1.40x, 1.29x and 1.18x. The rate covenantA promise in the bond documents that the issuer will set its charges high enough to keep net revenue above a stated multiple of debt service. breaks in year 3.

No, and saying so is what separates a credit answer from arithmetic. At 1.18x the bonds are still paid in full with Rs 21.8 crore to spare. A rate covenant breach usually obliges the issuer to raise tariffs or hire a consultant to recommend a new tariff, and the cure here is small: a 2.2% increase in year 3 restores 1.25x, and 10.1% restores the original 1.50x. The shortfall to the covenant is only Rs 8.2 crore.

The numbers are manageable; the behaviour is the risk. For a revenue bond the tariff decision is the credit, because the issuer controls the one lever that repays you. A council that freezes tariffs in an election year has shown that the covenant bends to politics. If the freeze ran about 4.5 years, cash would no longer cover debt service at all. The questions to ask are the corporation's history of tariff revisions, whether a state regulator can force increases, the size of the debt service reserve, and whether revenues flow into an escrow account the trustee controls. A reasonable view is stable today with a negative outlook, turning on the first tariff decision after the freeze.