To create the past-negative form of う-Verbs, first change the verb's final kana to the corresponding kana with an あ sound from the same row. An exception is verbs ending in う, which changes to わ. Then, attach the past form of ない or ます. This results in either なかった for the plain/casual form, or ませんでした for the polite form.

For the polite ませんでした form, the conjugation is slightly different. Instead of changing the final kana to its あ-sound equivalent, you will change it to the い-sound kana from the same row before adding ませんでした.

The past-negative tense is used to state that an event 'did not occur' or something 'was not the case' in the past.

• 彼(かれ)は私(わたし)を呼(よ)ばなかった。
  He didn't call me.
• 新(あたら)しい靴(くつ)は買(か)わなかった。
  I didn't buy new shoes.
• その音楽(おんがく)は聞(き)きませんでした。
  I didn't listen to that music.
• 冷蔵庫(れいぞうこ)には牛乳(ぎゅうにゅう)がありませんでした。
  There was no milk in the refrigerator.

A colloquial, semi-polite form can also be created. This is done by taking the plain form なかった and simply attaching です at the end. While not considered grammatically standard, this pattern is frequently used in daily conversation and is widely accepted by native speakers.

• 駅(えき)では待(ま)たなかったです。
  I did not wait at the station. (Notice the use of で and は together. Double particle usage is common when presenting a topic in Japanese)

ある is a special case that deviates from the standard conjugation rules for う-Verbs. Its plain past-negative is not あらなかった, but rather just なかった. However, its polite past-negative form, ありませんでした, conjugates normally as you would expect.

• 時間(じかん)がなかった。
  There wasn't enough time. (Casual Japanese past tense)
• 時間(じかん)がありませんでした。
  There wasn't enough time. (Formal Japanese past tense)