In addition to my full-time job, which I'm retiring from in less than two months, I do some welding on the side. I recently did a job for a machine shop. He dropped the machined parts off to me, ready to be fit and welded. I quoted him a price and he was fine with it. When he came to pick them up, I was expecting he was going to pay me. Instead he asked if I could invoice him. I said "sure". So, I e-mailed him an invoice. I put on it "Due on Receipt". A couple of weeks go by and nothing. I text him to see if he mailed payment. He said he would pay me in his next "billing cycle" and I should have payment by the end of this past week. Nothing yet. It hasn't been 30 days yet but we're getting close. I figure 30 days is standard business practice. I don't want to be a jerk because I plan on doing more of this type of thing after I retire. I have a two year business degree so I know how business is done, but I still feel like "I did the job, I want to get paid". I really don't care about his "billing cycle".