I almost always pay bills via recycled envelopes. (Some bills contain an envelope.) It takes a bit of time, but I have more of that, and I hate to waste. If there is a lot of writing on front, I toss them. Writing on back, not so bad.
There are at least two kinds of window envelopes, the window on right, where the address goes, and on the left. Just insert a blank piece of junk mail( –or the back of another envelope) to cover that space. To add the address, I hold white bond paper (fitted TO the envelope) to the outside, hold it up to light, and mark the four corners, giving an approximation of the address space. Write the address and stick it into the envelope.
I cover the upper left info with my own stick-ums and info, and on the bottoms, front and back—on the back, look for the long pale orange number near the bottom, left to center, and scratch over them with pen. Be sure to use a stick-um or pen on other black spaces on fronts, they are there for the company's reasons that have nothing to do with you.
Other envelopes become grocery or to do lists. Or doodle paper. Or...
