Schedule AI is needed to report unequal income, not unequal payments. Unequal payments just keep you from using the “short method” of Form 2210. The “regular method” doesn’t require extra record-keeping, and with tax prep software it should take no extra time or effort to fill out.
No disagreement here…………….just trying to respond to previous comment that equal payments aren’t necessary. They aren’t if you front-load the payments (pay faster than equal), but if you backload the payments (not OP’s case), there may be problems unless you can show that payments reflected timing of income.