Here’s an idea: what if bills came with a sweet treat, like a lollipop or something. Or perhaps if the bill itself was printed on editle paper, like ricepaper, using a food dye-based ink. Aside from the improved biodegradability of the paper, it’d also make you look forward to opening your bills and nibbling at them. Better yet, it’d encourage you to pay them, because then you wouldn’t need the paper copy any more and could eat them.
It’d certainly make large bills easier to swallow, anyway.
Psychologically speaking, it’d play upon the Reciprocity Norm, an observed phenomenon in which people who are given something are more likely to give something in return: when charities give you a free pen in the envelope they send you, or when Hari Krishnas give you a flower at an airport “as a gift” and then ask for a donation, they’re playing upon this principle. Would sucking on candy delivered to you as a “gift” from your electricity company make you feel guilty for putting off paying the bill for a few days longer than you should?