the past tense of ought to

[Unregistered]

Dear sir(s)

Gretings from Iran.
Would you pls let me know what the past tense of "ought to" is in indirect speech?

Best regards
Iraj

[Tdol]

It doesn't have a past tense as such. In indirect speech it can be used two ways:
He told me I ought to do it. (Here, he was giving me advice about the future)
He told me I ought to have done it. (Here, he was criticising me for me failure to do something before he spoke)