What's the idiomatic tense of verb to use in a TODO list?

Question

Suppose I have a TODO list with items meant to be read by myself in the future. Items include things like

• Buy milk
• Get groceries

and so forth. If this TODO list were translated to Japanese, what would the idiomatic tense of the verbs be?

• ミルクを買え (imperative, since TODO items are technically commands to oneself?)
• ミルクを買おう (volitional, to make it more encouraging?)
• ミルクを買う (non-past?)

I assume that since the TODO list is primarily meant to be read by one's self, no Keigo or formal conjugations would be required?

Answer 1

ミルクを買え and ミルクを買おう would be extremely uncommon though not wrong. ミルクを買う is fine but most people will probably shorten it to ミルク買う or just ミルク. You could also say ミルク購入 but in this specific case it would be uncommon because it's cumbersome to write 購.

Other examples would be:

• 部屋掃除 or 部屋掃除する
• 洗濯物の取り込み or 洗濯物取り込む
• 鍵返却 or カギ返す

Another possible form is ミルク買っとく which is close to ミルクを買え or ミルクを買おう but more common because it fits well with a TODO list (it's odd to say "Buy milk" or "Let's buy milk" to yourself, but "Better have milk" is a bit more natural to tell yourself IMO)

Answer 2

People usually won't use keigo in any sort of note to self, yes.

So if you're talking about shopping lists, most people will simply list itens in it; since it's a shopping list there's no need to write ～を買う anywhere. Here's an exemple I've found online by googling 買い物リスト:

Now for a ToDo list, people usually use 辞書形{じしょけい} (the dictionary form), e.g. 牛乳を買う or ホテルの予約をする, ゴミを出す. This is what I found googling for やることリスト:

命令形{めいれいけい} (imperative) would only be used in a note to someone else (hierarchically below self), not to oneself.