> As pointed out [here][1], **Michael Swan, Practical English Usage** indicates:
> 
> **Both verbs can be used in British English to talk about obligation.**
> (**In American English, *have to* is the normal form.**) British English
> often makes a distinction as follows. 
>
>**Must** is used mostly to talk
> about the feelings and wishes of the speaker and hearer for
> example, to give or ask for orders. 
>
>**Have (got) to** is used mostly to
> talk about obligations that come from "outside" for example from
> laws, regulations, agreements and other people's orders.


Also, **"Must you" is much more formal and as such rarely heard in speech, esp in AmE** {SPOK at COCA} these days.

E.g. at [COCA (CORPUS OF CONTEMPORARY AMERICAN ENGLISH)][2]

. DO YOU HAVE TO
 
in [SPOK]

52 hits

. MUST YOU

in [SPOK]

0 hits

I am using the "." as part of the query to look only for sentence starts.

>-

At the BNC (BRITISH NATIONAL CORPUS):

. must you

http://bnc.bl.uk/saraWeb.php?qy=.+must+you&mysubmit=Go

3 results

[At BNC

. do you have to

times me out and I'm talking to the Webmaster about it:-)]

For more **information on usage**, check this grammar forum discussion:

[**'have to' vs 'must'**][3]


  [1]: http://thegrammarexchange.infopop.cc/eve/forums/a/tpc/f/340600179/m/9161003183?r=4971003183
  [2]: https://www.english-corpora.org/coca/x.asp?r1=&w=1120&h=700
  [3]: http://thegrammarexchange.infopop.cc/eve/forums/a/tpc/f/340600179/m/9161003183?r=4971003183