Private Research — ruling 1

Putting on a counter is optional. If you forget, you can't go back later even if it is something you usually do.

Private Research : règles, fonctionnement et interactions (MTG)

Private Research is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Enchant creature At the beginning of your upkeep, you may put a page counter on this Aura. When enchanted creature dies, draw a card for each page counter on this Aura.

How it works : Private Research

Original English text — Wizards of the Coast / Scryfall

#1October 4, 2004· Wizards of the Coast
Putting on a counter is optional. If you forget, you can't go back later even if it is something you usually do.
No other card is named in this ruling.