The one-tense-further-back rule
There is a general rule which says that when we use a reporting verb in the past, as above, the verbs used in the original speech are usually moved one tense further back. Thus:
This happens because the time and place where we are reporting the action are different from where the original words were spoken. See what happens in the following examples and note the pitfalls:
will / shall future = would
is going to future = was going to
can / may = could / might
present progressive = past progressive
present simple = past simple
present perfect = past perfect
past simple = past perfect
present and future patterns
The Prime Minister said: 'I shall co-operate fully with the enquiry.'
The PM told the press that he would co-operate fully with the enquiry
(Take care to use would when reporting future shall / will. If we used should here, it would suggest obligation and that is not what is meant.)
'You don't look very well. You should really stay in bed today.'
I told her she didn't look very well and should really stay in bed.
I advised her to stay in bed.
(Note that there is no past form of the modal verb should, meaning obligation, so it cannot move one tense further back.)
Similarly there is no past form of could for future requests, so it cannot move one tense further back either. The same applies to might for suggestions:
'Are you going shopping this afternoon? Could you get me some toothpaste?'
I asked her if she was going shopping and could get me some toothpaste.
I asked her to get me some toothpaste if she was going shopping.
Compare this with the way in which can changes to could:
'We might go out for a drink later on, if you're free.'
They suggested we might go out for a drink later, if we were free.
'I can't read this small print without my glasses.'
He admitted that he couldn't read the small print without his glasses.
'How did you find your way here in the dark? The paths are not marked.'
I asked her how she had found her way here as the paths are not marked.
(Note that because the lack of paths is an ongoing situation, we would probably retain the present tense even in the reported situation)
Past perfect remains past perfect
'We've met before, haven't we?' ~ 'No, I don't think we have.'
He thought we had met before, but I was quite sure we hadn't.
Like should / might / could in the earlier examples, the past perfect used in direct speech cannot move one tense further back in indirect speech:
On-going situation: no tense change
'If only I had taken your advice, I would have saved myself a lot of money.'
He regretted / was sorry that he hadn't taken my advice.
He admitted that had he but taken my advice, he would have saved himself money.
We have already noted an instance of this in the 'paths' example, above. Here are two further examples of where it may or may not be appropriate to change the tense:
When reporting verb is in present or future: no tense change
I told her that I love her…and hope to marry her one day.
I told her that I loved her…but it was a lie.
Daughter: I'm going out now, dad.
Mother (out of earshot): What did she say?
Father: She said she's going out.
Granny: Where's Jenny?
Father: She's out.
Granny: She didn't tell me she was going out.
Father: She told me she was going out.
Note that when we use present or future reporting verbs, the situation we are reporting has not changed, so there is no tense change:
She wants to know where Paul is.
'Did he phone?'
I don't know if he phoned.
'Has he left already?'
I don't think he's already left. No.
'We've got tickets for the match, so we'll be able to join you.'
I'll tell Kevin you've got tickets and will be joining us. He'll be well pleased.
'I shall not be resigning over this issue.'
A spokesman from the Ministry has confirmed that the Minister will not be resigning over this issue.