I forgot to write an iou when I borrowed money. Can we write it later? How to write without writing?

Borrowing money is not writing IOUs, but writing IOUs. There are different legal restrictions on IOUs and IOUs. For example, the IOU may be due to the fact that I bought something without paying the full amount, but owed a part of the payment. It seems that the written IOU has only three years of legal limitation, and it will have no legal effect after three years. However, the statutory limitation of IOUs is relatively long, that is, 20 years, and it will be invalid after 20 years. If you forget to write an IOU when borrowing money, you can write it later. Be sure to write down the date of borrowing at that time. The date of signature can be written according to the date of borrowing, or according to the date written, but it must be stated that this is a written loan. Because the date of writing the loan is inconsistent with the date of borrowing, it is necessary to explain the reason.