When is 4NT Quantitative?

I received a question today asking for some rules of when 4NT should be Quantitative (non-forcing slam invite) or not.

Here's my reply:

One should start with these basic rules:

4NT is always quantitative directly over any NT

4C is always Gerber directly over any NT

4NT is always ace/keycards asking if not over NT, and the opponents have not bid at the 4 level at some point

4NT is takeout if over 4 of a major by the opponents

4NT is to play if over 4 of a minor by the opponents

If the opponents have bid at the 4 level at some point, but are not the last person to make a non-pass, 4NT is natural

Then add in new rules for when 4NT can be quantitative over suit bids

For example:

4NT is quantitative if the 4NT bidder could have easily set trumps, and then asked for aces/keycards

Example: 1NT-4D(transfer);-4H-4NT asks for aces/keycards, and thus 1NT-2D(transfer);-2H-4NT is quantitative

a subset of this rule:

4NT is quantitative if there is a bid that shows a game forcing hand/slam try in the last suit, and it is forcing.  Thus if 1NT-2C;-2H-3S would be an artificial slam try in Hs, 4NT instead of 3S would be quantitative.

Only put these detailed types of rules in if you are playing at top levels - not required for clubs and small tourneys.

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Memphis mojo comments:

If it goes:

3C dbl pass 4NT,

what does 4NT mean given your rules?

Answer:

By my simple rules, it is ace/keycards asking, however you define it for your partnership with no suit agreement.

Here this is another case where a partnership can implement a detailed rule, such as:

When opponents have opened a preempt, a bid of 4NT by opener or responder is natural, if neither player has cuebid, and there is no suit agreement.

Then 3C-Double-Pass-4NT would be natural, a hand too good to just bid 3NT, non-forcing but having slam interest.